Information

Why do lychee seeds come in different shapes?


I've been eating lychee fruits recently and noticed that every once in a while (in about 1 of 10 fruits or so) the seed in the fruit is shriveled, while in other fruits from the same batch the seeds have regular ellipsoid shape:

Top: regular seed, bottom: shriveled seed

The fruits with the shriveled seeds don't look or feel or taste any different from those with the regular seeds.

It seems like a binary trait, i.e. seeds are not more or less shriveled, they are either shriveled or not.

Why are the seeds so different? Do they come from different cultivars, or it's some kind of Mendelian development, or maybe some kind of a plant disease?


The shrivelled seeds are aborted seeds, known as 'chicken tongues'. Some cultivars of lychees mainly produce fruits containing chicken tongues. These cultivars are usually considered more desirable, because they have more flesh.

Source: https://www.crfg.org/pubs/ff/lychee.html


Why do lychee seeds come in different shapes? - Biology

The lychee ( Litchi chinensis Sonn ) an important sub-tropical evergreen fruit crop belonging to family Sapindaceae, is believed to have originated in China, where it has been grown in Southern Guangdong state for thousand of years. It is highly specific to climatic requirements and probably due to this reason its cultivation is restricted to few countries in the world. In India, lychee was introduced in the 18 th century through Burma, and from there, it spread to many countries. India and China account for 91 percent of the world lychee production but it is mainly marketed locally. In India, 428,900 metric tonnes of lychee is produced annually from 56,200 hectares. Lychee being exacting in climatic requirement is confined to a few states with 74 percent of production recorded in Bihar. In this state, lychee is the livelihood for millions of people as it provides both on-farm and off-farm employment. Small and marginal farmers get additional income from lychee plants in their homesteads. Thus, lychee cultivation is the livelihood security for a large population, especially in the state of Bihar.

The lychee tree is handsome, dense, round-topped and slow growing with evergreen leaves having 6-9 elliptic oblong and lanceolate abruptly pointed leaves. Colour of leaves varies from light green to dark green. Greenish white or yellowish flowers are borne in clusters. Fruits are round or heart shaped having thin, leathery skin. The colour of fruits varies with cultivar, and is red or rose or pinkish. The edible portion or fruit is the aril, which is immediately beneath the skin. Flavour of the aril varies with cultivar, which is distinctive. Seeds are bold but in some cultivars seeds are partially developed, due to failure of pollination, referred to as ‘chicken-tongue’ seed. The trees with small seeded fruits are prized because of the greater portion of pulp.

Considering the importance of this fruit crop in the region, efforts are made to provide technological support through research and promoting production, post-harvest management and marketing, including export, through development programmes. Lychee has also been identified as an important crop for export. Currently, Indian export of lychee remains quite small due to expanded domestic market. The product for export and distant domestic markets is typically packed in 2 kg cartons after pre-cooling and sulphuring. Domestic marketing generally receives lychee in 10 kg wooden cages or 15 to 18 kg baskets. The growing of lychee in different states under various climatic conditions has advantages in terms of earliness and extended harvest. With a narrow genetic base, under given climatic conditions, fruits are available only for 3-4 weeks. However, due to the spread of cultivation over a wide range of climate there is possibility for extending the cropping period from the first week of May to the first week of July. Evidently, with an expanding market, there is ample potential for increasing area and production with improved production technology and efficient post-harvest management and storage. This paper deals with the current status and identifies the constraints which are required to be addressed.

2. PRESENT SITUATION OF LYCHEE CULTIVATION IN THE COUNTRY

In India, lychee ranks 7 th in area and 9 th in production among fruit crops (Table 1), but in value terms, it ranks sixth. At national level banana and mango are the most important fruit but in Bihar state, lychee is considered to be the most important fruit as it contributes significantly to its total fruit production.

Table 1. Area and Production of Major Fruit Crops in India

There has been substantial increase in area and production of lychee in the last 50 years. Area has increased from 9,400 hectares in 1949-50 to 56,000 hectares in 1998-99. The contribution of lychee to total area under fruit has increased from 0.75 percent to 1.5 percent. Increase in area between 1991-92 and 1998-99 (7 years) has been 14.28 percent, while production increase during the same period is to the tune of 75 percent. Productivity also recorded an increase of 52.91 percent during the same period. Evidently, production and productivity of lychee is constantly increasing in the country.

Lychee being exacting in climatic and soil requirements has limited distribution. It is grown in the states of Bihar, Tripura, West Bengal, Uttar Pradesh, Punjab and Haryana. Of the total production of lychee in India, 74 percent is contributed by Bihar. The second largest lychee producing state is West Bengal followed by Tripura and Assam (Table 2). Productivity is highest in Bihar followed by West Bengal. An interesting feature of distribution of lychee in India is that maturity commences first in Tripura, followed by West Bengal then Bihar. The first and second week of May is the time for harvest in the eastern region, while lychee of Bihar matures in the 3 rd -4 th week of May and continues up to the first week of June. Lychee in Uttar Pradesh and Punjab is ready for harvest during the 2 nd - 3 rd week of June. In Himachal Pradesh, lychee of the same cultivar is harvested in the last week of June. Interestingly, in most of the states the best lychee orchards are seen along the rivers, big or small.

Table 2. Area and Production of Lychee in different States

Lychee varieties grown in India are highly variable under different climate and soil conditions. Singh (1954) described 33 varieties and classified them into 15 groups varieties of lychee grown in India have also been subsequently described (Singh, 1998). When distinguishing the cultivar, the shape of skin segments and protuberances are the reliable and stable genetic characteristics. Fruit size, shape and taste are also variables but are influenced by other than genetic factors. Indian cultivars vary greatly in vegetative flushing pattern, flush colour and flowering ability. Based on these characteristics, cultivars were classified in five groups (Singh, 1998). Group A, which has 7 cultivars is the early group, B and C groups are mid-season, and group D is the late group. Only one cultivar, which is very late, is under group E and its cultivation is confined to Muzaffarpur. Yield and physicochemical characteristics of important cultivars are given in Table 3. The cultivars also show variation in yield, cracking, and physico-chemical quality. Shahi among the early group and China among the mid-season groups appeared to be promising in Jharkhand state (Babita, Personal communication).

Leaf colour along with shape and size of the leaves is of importance in varietal identification. The leaf of Rose Scented is boat-shaped while China has a distinctive twist along the length curved upward from the midrib and down along its length. Small leaflets of Bedana are oval shaped. The fruit shape of the lychee is very distinguishing. The round shape of Bedana is distinguished from the oblong shape of China or Shahi. The fruit is smooth and pulp is even or uneven. The apex of the fruit can be round, obtuse, blunt as in Shahi, or pointed as in China. The varieties can also be distinguished depending upon the colour of the new flush and season of flushing. Shahi produces very light coloured flush while China has pinkish flush. Bedana has very dark pink flush. Emergence of the panicle and its shape also differs. Singh and Singh (1954) distinguished the cultivars based on panicle characteristics. Shahi has long panicles while Bedana produces short and compact panicles. The colour of the lychee fruit is pinkish brown or dark red depending on the cultivar. Colour of the skin varies and is also influenced by growing conditions.

Table 3. Physicochemical characteristics of important cultivars

Estimated Fruit Yield (Kg/ plant)

Skin thickness depends on the cultivars. Bedana and China have very thick skin. Rose Scented and Shahi have very thin skin. Skin surface at maturity also varies being smooth, swelling, sharp and pointed. Protuberances of the skin (pericarp) can be smooth and sharply pointed. Bedana has very smooth protuberances while Shahi has very distinct protuberances. The presence and absence of seed as well as structure and size of seeds also vary from cultivar to cultivar, although it is influenced by environmental conditions. In Rose Scented and Bedana, a high proportion of chicken-tongued, seeds (aborted seeds) are observed while China has bold seeds. In a recent selection cv. Swarna Rupa, a high proportion of fruits have small seeds (Singh and Yadav 1992). Although lychee has short duration not exceeding 30-40 days, cultivars can be distinguished based on season and maturity, provided they are grown at same location. Accordingly, cultivars can be grouped into three categories namely, early, medium and late season. Fruit maturity also varies slightly and relatively from year to year depending upon prevailing weather conditions. The maturity period of the fruit also varies depending upon agro-climatic regions. Some of the varieties in West Bengal come to maturity earlier, while the same varieties can be late in Uttar Pradesh. Due to the production of lychee in varying agro-climatic conditions, maturity, fruit colour, shape and size are reported to be varying. Thus, there has been much confusion in the names of varieties. As a result, the same variety is called by different names at different locations (Ray et al. 1984). Varieties grown in India are given in Table 4 and a few selected varieties are described.

Table 4. Varietal Distributions of Lychee in Different States in India

Deshi, Purbi, China, Kasba, Bedana, Early Bedana, Late Bedana, Dehra Rose, Shahi, Manragi, Maclean, Longia, Kaselia and Swarna Rupa

Early Large Red, Early Bedana, Late Large Red, Rose Scented, Late Bedana, Calcuttia, Extra Early, Gulabi, Pickling, Khatti, Dehra Dun, Piyazi

Bombai, Ellaichi Early, China, Deshi, Purbi and Kasba

Early Seedless, Late Seedless, Seedless-1, Seedless-2

This is the most popular cultivar grown in North Bihar, Jharkhand, Uttaranchal and Uttar Pradesh regions of India. Besides having high quality fruit it has a distinct rose aroma and hence is called ‘Rose Scented’. It is known as Shahi in Bihar, Rose Scented in Uttaranchal and Muzaffarpur in Western Uttar Pradesh. The vegetative flush of this cultivar is light, and fruit weight ranges from 20-25 g. This cultivar is earliest in maturity, and ripens during the second week of May to the first week of June at various locations. It matures on 12-15 May in Jharkhand, the 25th May in North Bihar and by the first week of June in the Terai region of Uttaranchal. Trees of this cultivar are very vigorous and produce fruits ranging from 100-150 kg per plant. Mature fruits are prone to cracking in zones with low humidity and poor moisture content in the soil. Fruits are globous-heart or obtuse in shape having rose madder and fuchsia purple background with red tubercles at ripening. Pulp is greyish-white, soft, moderately juicy and sweet, and TSS ranges from 19.00 to 22° brix. Seed size varies. On the same plant larger fruits have big seeds while seeds in small fruits are shrunken. The fruits are known for excellent aroma and quality. This cultivar occupies a major area under lychee in India.

The origin of this cultivar is not known but the name indicates that it was selected for its superiority and named ‘China’. It is tolerant to hot waves and fluctuations in soil moisture, which cause fruit cracking. It is known as Purbi, Calcuttia, Bengalia, Bombaiya and Manragi in different regions. This is a medium-late season cultivar. Fruits ripen during the end of May in West Bengal, the first week of June in Jharkhand and North Bihar and the third week of June in Uttar Pradesh. Trees are comparatively dwarf and high yielders but it is prone to alternate bearing. Rains at the time of fruit bud differentiation cause emergence of vegetative flush resulting in loss of crop. It bears fruits in cluster of 12-18. In some cases more than 30 fruits per cluster are also recorded. The plants bear less fruit in eastern and southern directions. Fruits are large in size, medium-heavy in weight, oblong in shape, and tyrant rose in colour with dark tubercles at maturity. The aril is creamy-white, soft, juicy, sweet having 18 to 17° brix TSS, 11 percent total sugar and 0.43 percent titratable acidity. Seeds are glaucous, dark chocolate in colour, oblong to concave or planoconvex in shape, medium in size (2.9 cm length and 1.5 cm diameter), and average in weight (3.49 g/seed). The ratio of rind:pulp:seed by weight is 16.42 : 69.22 : 14.36 (Pandey and Sharma, 1989). The flavour of the pulp is not pleasant like Shahi, but owing to its high yield and no cracking this cultivar is popular. This cultivar cannot be distinguished from Manraji and Purbi grown in the eastern part of Bihar state.

It is also known as Early Seedless in Punjab because of its early ripening and small seeds. This cultivar has distinguishing leaf and flower characters. The cultivar is very much popular in Uttar Pradesh and Punjab. Trees are medium, attaining an average height of 5.0 m and spread of 6.2 m. It is a medium yielding cultivar (50-60 kg/tree) but bears fruits regularly. Fruits are medium in size and weight ranges from 15 to 18 g having oval or heart shape, rough surface with uranium green skin covered with carmine red tubercles at maturity. Aril is creamy white, soft, juicy and sweet containing 17.2 to 19.8 0 brix TSS. Seed is very small, shrunken, glamorous, dirty chocolate in colour. The overall fruit quality of the cultivar is good.

This cultivar is also known as Late Seedless. This is a late maturing cultivar, which usually ripens, in the last week of June in Uttaranchal, the end of May in Jharkhand and in first the week of June in Muzaffarpur. The trees are vigorous having an average height of 5.5 m and spread of 7.0 m., with yield ranging from 60-80 kg/tree. Although the fruit size is medium the pulp content is high. The fruits are conical in shape and vermilion to carmine in colour having dark blackish brown tubercles at maturity. The pulp is creamy white, soft, juicy, sweet having 18 to 2° brix TSS, but acidity is low. Seeds are very small, shrunken, glamorous, and chocolate in colour with fusiform shape. The new flush is dark pink in colour and its leaf can be distinguished from other cultivars. The panicle is compact.

This is an early maturing variety selected from Ajhauli village. It yields about 80-100 kg fruit from a sixteen year old tree. Fruits are red in colour weighing 15 to 18 g and have big seeds. It cannot be distinguished from Shahi on vegetative characteristics as it has many similarities. This variety is highly prone to cracking but under irrigated condition cracking is minimized.

This is an important cultivar in West Bengal. It is a vigorous cultivar attaining a height of 6-7 m and spread of 7-8 m. The cultivar matures early (second week of May) and gives 80-90 kg fruit yield per tree. Fruits are large in size (3.5 cm long and 3.2 cm diameter), obliquely heart shaped, and weigh 15-20 g. The colour of ripe fruit is an attractive carmine red with uranium green skin background. Like the Chinese cultivar ‘Nuomici’, this cultivar also has a tiny under-developed fruit attached to the fruit stalk of each fully developed fruit. The pulp is greyish white, soft, juicy, sweet, containing 17° brix TSS, 11 percent total sugar and 0.45 percent acidity. The elongated, smooth and shining seed of light chocolate colour is 2.3 cm long, 1.6 cm in diameter and weighs 3.4 g. This cultivar is akin to China grown in other states.

This is an important cultivar of Uttar Pradesh and Punjab where it is grown with the name of Dehra Rose. The fruits start ripening by the third week of June in Uttar Pradesh but in Jharkhand it matures with Shahi. It is a medium vigorous tree (5 m height and 7 m spread) which produces medium to high yield. Fruits are medium to large in size, measuring 3.7 cm in length, 3.5 cm in diameter, weighing 15.2 g and having oblique-heart to conical shape. Bright rose-pink coloured fruits of Dehra Dun look very attractive at ripening. The pulp of this cultivar is greyish-white, soft, moderately juicy with 18° brix TSS, 10.4 percent sugar and 0.44 percent acidity. Seeds remain small, light, shrunken, mostly oblong in shape and dark chocolate in colour. Under rainfed conditions this cultivar is highly prone to cracking. The name of the cultivar suggests that it is a selection made in Dehra Dun.

This is another late maturing cultivar of North India in which ripening takes place by the fourth week of June. Early rain hampers the quality of fruits. The medium vigorous tree of cultivar Gulabi bears profusely and regularly with medium to large sized fruits. The shape of the fruit is variable from oblong-oval to heart shaped whereas the rind colour at ripening varies from shrimp red to carmine red with mandarin red tubercles. The pulp is firm, greyish white, sweet with 18.2° brix TSS, 10.7 percent total sugar and 0.49 percent titratable acidity. The seed is rather big, heavy, oblong-cylindrical in shape with a shining chocolate seed coat.

This is an important cultivar in West Bengal having brighter prospects for commercialization. The trees are moderately vigorous, attaining an average height of 5-6 m and spread of 6-7 m. It is a mid season cultivar which ripens in the first week of June. The cultivar yields 50-60 kg fruits annually. Fruits are conical, marigold-orange red in colour with an average weight of 12-15 g. The pulp is creamy white in colour, sweet, soft and juicy with agreeable flavour. The cultivar has 18° brix TSS, 11.5 percent total sugar and 0.45 percent acidity, and 6.91 :1 pulp:stone ratio at ripening. Seeds are relatively small, shining, and weigh 1.5 - 2.0 g. Fruits are less susceptible to sunburn and cracking. This cultivar has not assumed commercial success.

This cultivar is well distributed in North Bihar, and is preferred for late maturity. The tree is medium in size, leaves are small and light in colour and it has compact panicles. Fruits are medium in size and the aril has an excellent aroma. Due to shy bearing habit, there is a declining preference for this cultivar.

This is a large fruited cultivar selected from Kasba village for its attractive fruit size and colour. The tree is large and compact having broad and elongated leaves. Fruit weighs between 23-27g, perhaps the heaviest fruit among the known varieties, but the number of fruit is less. Interestingly, the cultivar performs better in marginal soils as it has the capacity to absorb more nutrients (Personal Communication, S. Babita).

This is later maturing cultivar found growing in isolation. The tree is medium in size and fruits mature very late. Fruit attain a pink red colour. The pulp content is comparatively low and the seed is big. This cultivar is also known as ‘khatti’ or ‘pickling’. The cultivar has not assumed commercial success.

This is a late maturing, cracking resistant cultivar of lychee selected at the Central Horticultural Experiment Station (CHES), Ranchi. The fruits are a attractive red colour with small seed and high aril percentage. Leaves are similar to Bedana in shape and size. New flush is pink and mature leaves are dark in colour. The cultivar has 18.5-22.5 cm long, compact panicles. Fruits are medium in size weighing 12-15 g and have a high pulp content. The pulp contains high TSS and low acidity. Total sugar content in the fruit is 13 percent out of which 8.5 percent is reducing sugar. The cultivar is suitable for extended harvest as it matures after China and is prized for its attractive fruit colour. This cultivar is recommended for commercial production.

This is a late maturing selection from the population of the China group. It bears fruits both at the outer and inner canopy, which helps in reducing the sunburn as well as fruit cracking. The fruits are deep red, conical shaped and appear in a cluster of about 15-20. The fruit has an average weight of 21.3 g containing 3.8 g seed and 16.1 g pulp. Vegetative characteristics are similar to China however flowering and fruiting is earlier.

The cultivars described above can be grouped based on the flush colour, shape of the leaf, panicle, fruit, pulp colour and flavour and maturity. Accordingly a key to important cultivars of lychee has been prepared and is presented in the Table 5. All the major cultivars fall into five groups.

Table 5. Key to Important Cultivars of Lychee

1. Flush pink, leaf boat-shaped, dark green, panicle long, fruits oblong with round apex.

-Colour of fruit deep pink

-Colour of fruit light and greenish

-High cracking and big seed

2. Deep pink flush, leaf with twist along the length, curved upward from the midrib and down along their length, panicle long, fruit oblong with pointed apex

3. Dark pink flush, oval shaped leaves, compact and small panicles, Fruit round, smooth, chicken tongue seed (aborted seed)

Early bedana or Early seedless

4. Deep pink flush, boat-shaped and dark green long leaves, panicle long, largest size fruit, deep in colour

5. Small elongated leaves, light green in colour, panicle compact, fruit medium in size, very late maturity.

-Pulp sweet and excellent flavour

Since, flower bud differentiation, flowering, fruit set, fruit quality and flavour development in Lychee is influenced significantly by temperature and humidity, it has adapted well in the sub-tropics where summer months are hot and wet and winter months are dry and cool. Hot summers free from hot wind and winters free from frost are essential.

Lychee cultivation is highly successful in areas having minimum temperature of 10°C from December to February and 38°C from April to June. However, temperature of 32° C during these months is considered to be optimum. It is highly specific to climatic requirement for its establishment, plant growth and fruiting, and consequently spread of area. A moist atmosphere, occasional rainfall, cool dry winter free from frost and hot winds are ideal for its cultivation. In lychee growing areas in India the temperature varies from 21° C to 37.8°C during flowering and fruiting. It has been observed that flower initiation in lychee requires comparatively low temperature. Seasonal variation in temperature is favourable for proper fruiting. A dry climate, free from rains for about 2 months before flowering induces flower bud differentiation, blossom and consequently give high production. In Chotanagpur, the fog free dry winter, mild sub-tropical summer and intermittent pre-monsoon showers during April-May have been observed to be highly favourable for blossoming, better aril development and improvement in fruit quality. The sub-tropical to mild temperate climate in the foothills and valleys of the Himalayas are also suitable for lychee cultivation. Depending upon the temperature rise after winter the time of flowering and maturity is determined. No fruiting has been recorded when lychee has been grown in tropical conditions. However, on hills in southern states flowering is observed and harvesting commences in November-December.

In India, lychee is grown successfully on a wide range of soil types, which include sandy loams, laterite, alluvial sand, and calcareous soil, but the best lychee orchards are seen in alluvial sandy loam soils with good drainage and access to the water table. The performance of orchards is very poor on clay soil with poor drainage. Lychee grown in sandy soils have a root system network, while trees grown in clay soil have very poor root distribution. The pH of soils in North Bihar ranges from 7.5 to 8, while in Jharkhand lychee grows well at a pH of 6 to 6.5. It grows well even in calcareous soil with 30 percent free lime content. However, in acidic soil of Jharkhand mycorrhizal activity is minimal which affects fruit yield and quality (Pandey and Mishra, 1975). The taxonomy, morphology and mycotrophic habit of mycorrhiza association with lychee was described by Pandey and Misra (1975) and their work also confirmed that lychee requires mycorrhiza to grow and produce better quality of fruits. Thus, it is often suggested that new orchards should be grown with the introduction of soil from old orchards.

3. PRODUCTION OF PLANTING MATERIAL

Lychee is generally multiplied by vegetative methods of propagation as plants raised through sexual method (by seed) grow slowly, have a long juvenile period and do not produce fruit true to the type. However, earlier introduction in different parts of the country was perhaps through seeds, which enabled the selection of superior types and perpetuation the cultivar through vegetative means. The most commonly practiced method of vegetative propagation is air-layering, though cutting, grafting and budding have been found to be successful.

Air-layering, known as ‘marcottage’ in China and ‘goottee’ in India, is commercially practiced for large scale multiplication both in public sector and private sector nurseries. When and how this practice was adopted is not documented but the process of development and modification in the method of layering suggests that the method has gone through transformation. Earlier layering was done using clay soil having provision of watering, however, the air-layer practiced now uses growth hormone and nutrient mixed media of peat moss or coir pith, which is covered with polythene. For preparation of the air-layer a healthy terminal branch receiving good sunshine with a thickness of about 1.2-1.5 cm is selected and a 2.5 cm ring is made by removal of bark about 45-50 cm below the apical growth. The cambium layer is rubbed off and the woody portion is exposed. Rooting hormone (1000 ppm IBA) is used as paste or powder. A layer of moist sphagnum moss or coir pith is placed and wrapped with a piece (20 x 25 cm) of 400 gauge polythene sheet and tied properly at both ends to ensure supply of proper moisture which facilitates the development of roots. It is advised to enrich the rooting medium using organic nutrients. After about 50-60 days, the adequate root system develops from the upper end of the ring, which is visible through the polythene film. The layer is removed by making a sharp cut about 5 cm below the lower end of the ring, preferably in 2-3 stages. The detached layers are planted in partial shade. Success in rooting of the layer is determined by temperature and humidity. When night-time temperature falls to less than 20°C the root becomes brittle. Thus, June is considered to be best time for air-layering. In order to enhance the success of the detached layer, defoliation of leaves up to 50 percent is advocated. At the time of planting excess vegetative growth may be removed to maintain balance between the top and newly developed root system. Regular irrigation and weeding is done to facilitate better establishment and growth. Beds are kept weed free. Lychee layers become ready for field planting in 4-5 months. Growing of layers in the greenhouse has been found to enhance success.

Some nurseries practice, pot layering wherein a lower branch of mature wood is cinctured and the cut surface is buried in a pot or container filled with rooting medium. The pot is watered regularly. The roots develop in the cinctured portion of the branch in about 2 months. Then the branch is detached from the main plant by giving sharp cut, preferably in 2-3 stages. No repotting is required before transplanting in the field. Application of IBA (2000-5000 ppm) improves rooting and survival of the layers.

For large scale multiplication stooling is also recommended. In this method, planting is done closely at 1 x 2 m. Once the plant attains the required growth it is headed back to the stump during January-February which permits new shoot (stools) emergence from the stump within two months. A ring of 2 cm is made at the base of the newly emerged shoots and rooting hormone is applied. Then a mound of soil is raised around the shoots to encourage rooting and watering is done regularly. Profuse rooting occur in the stools within two months. These stools are detached and kept in the nursery for hardening and become ready for transplanting in July-August. In stooling, one must be careful not to allow the soil mound to dry, otherwise the rooting process is affected adversely. Therefore, the stool beds should be irrigated at weekly intervals from April-June.

Although this method is advocated it has not been practiced by nurserymen on a commercial scale. The propagation of lychee has also been tried through cutting under mist conditions. A high percentage of rooting was also obtained from the cutting treated with IBA and planted in April-May under mist. But this has not been adopted commercially.

Grafting in lychee is mainly practiced for changing scion cultivar or seedling tree or unproductive and old orchards by top working. The apical, side and approach grafting are mainly practiced. In apical grafting 10 cm long scion wood (non-terminal) with at least 2 slightly swollen buds gives better results. The technique of splice or tongue grafting is successful. Apical grafting has not been commercially used for large scale multiplication. Grafting appears to be promising provided seedling growth and percent germination improves. Yadav and Singh (1988) observed that the highest germination of lychee seeds could be obtained if fruits are harvested one week before maturity. A higher rate of growth in seedlings is possible under greenhouse conditions. Softwood grafting has been found to be successful in many nurseries. Budding of lychee has also been successful. However, much more work is required to be done before these methods become accepted practices.

Since, air-layering is a commercial practice, a large number of private nurseries have come forward for large scale multiplication of plants especially in lychee growing regions. It is estimated that about 300,000 lychee plants of different cultivars are produced annually. The regulatory framework to ensure the quality of plants is not in place, thus the creditability of public institutes or private nurseries determine the preference of growers. The cost of plants also becomes a factor in determining the preference of farmers.

4. ESTABLISHMENT OF ORCHARDS

Orchard establishment is a highly specialized activity, which requires proper planning, selection of site, land preparation, layout, planting of saplings, as well as orchard protection and management.

Selection of site and soil

Lychee can be cultivated in a wide range of soils, starting from sandy to clay loam with good drainage and rich in organic matter. However, well-drained deep sandy loam soils having good moisture holding capacity, rich in organic matter and calcium content have been found ideal for lychee cultivation. The well-drained soils of North Bihar rich in calcium content have been observed to be most suitable for better growth and quality fruits. The rolling uplands of Chotanagpur have also been found to be suitable. Soils with poor physical conditions, lacking in available nutrients can be improved for lychee cultivation by adding sufficient quantities of decomposed farmyard manure (FYM), compost and green manure. Lychee growth is restricted in clay soil, thus the site selected should have the above characteristics. When selecting the site climate is also given due consideration. Lychee should not been grown in excessively humid regions when winter temperature is not below 12°C. Also when selecting a site the source of water and transport facilities should be given due consideration.

Before layout the land is cleared of bushes and other weedy vegetation and is leveled with a mild slope in the opposite direction of the water source. To improve the fertility of the soil organic matter is added. A green manure crop is grown and incorporated into the soil, which improves its fertility, moisture holding capacity and physical condition.

Pits 90 x 90 x 90 cm in dimension are dug at the spacing decided for the orchard. Pit opening is normally recommended in April-May to have a sterilization effect for about 3 days. Before the onset of monsoon pits are filled with topsoil mixed with about 40 kg decomposed compost, 2 kg neem/karanj cake, 1 kg bone meal/single super phosphate and 200-300 g muriate of potash. Incorporation of about 2 baskets of soil from the root zone of old lychee trees encourages the mycorrhiza growth. Then the soil is allowed to settle with the first few rains and leveled properly. Planting is done during June to July. At the time of planting a hole the size of ball of earth is made in the centre of the pit at the marked point where the plant is fixed and the soil is pressed to remove air. Watering is done immediately after planting for proper establishment. Subsequently the plant is regularly irrigated till it is properly established.

Spacing and planting system

Lychee is an evergreen spreading tree, which attains the height of about 10-12 m at its full growth and development. Light penetration of its canopy is also desirable for proper fruiting, hence planting in square system at a distance of 9-10 m within and between the rows has been practiced. However, in an experiment conducted at the Central Horticultural Experiment Station, Ranchi, planting of lychee in a double hedgerow system at a distance of 4.5 x 4.5 x 9 m accommodating 329 plants/ha has been found to be the best and gave higher yield of equally good quality fruits up to 16 years of plantation. High density planting adopting a double row system has also been found to be superior at other locations in terms of yield and quantity of fruits. Through appropriate canopy management high density planting accommodating about 1,200 plants per hectare could also be done as has been found successful in mango. However, this would need further investigation.

Training of the plant in the initial stage is essential to provide the required framework. Unwanted branches should be pruned to provide definite shape and to promote growth of the trunk and crown of the tree. Three to four branches 60-75 cm from ground opposite to each other are allowed to form the proper frame of the tree. Further, crowded and crisscross branches are removed to facilitate better growth. The branches with narrow angles are also avoided as they are prone to breakage. Non-fruiting unproductive branches inside the canopy in growing and mature trees should also be pruned. Dried, diseased and scissors-shaped branches should also be periodically removed. Light pruning after harvest has been found congenial for better growth, fruiting and yield. While harvesting the fruit the panicle is plucked along with 8-10 cm of twig to promote new flush and better bearing for the succeeding year.

Among the several factors associated with production of lychee, balanced nutrition is considered to be the most important which determines productivity and quality. Lychee responds to exogenously applied manure and fertilizers and response varies depending upon cultivar (Kotur and Singh, 1993), climatic conditions and soil types. A survey conducted in the Doon valley indicated that 80 percent of orchards are low in N and P and need N and P application (Kunwar and Singh, 1993). In West Bengal, NPK was reported to be below the optimum level (Rao et al , 1985). However in Punjab N, K, Mg, Zn and Mn are reported to be in deficit range. Recently, a survey conducted by Babita (Personal Communication) has clearly shown that low yield and poor quality fruits in lychee are associated with a sub-optimal range of nutrients. Variation in nutrient content was also observed among varieties.

Field experiments conducted on different cultivars at different locations have clearly demonstrated the effect of a graded dose of NPK on growth, yield and quantity of fruits. Application of 600-800 g N, 200-300 g P 2 O 5 and 400-600 g K 2 O per plant is recommended for 12-15 year old trees. Nitrogen and Potassium should be applied in 2-3 splits and P 2 O 5 in two splits. Excessive application of nitrogenous fertilizer before flowering should be avoided. Phosphorus application at the time of flower bud differentiation improves flowering and fruiting. Application of cakes and manure is generally practiced to get better quality fruits. In general, lychee orchards maintained with higher doses of organic manure have better yield and quality as compared to orchards maintained with chemical fertilizers.

Additional application of Ca, Zn, B, Cu and Mn is recommended. Application of 0.6 percent Ca as calcium chloride improves fruit weight and quality. Zn is applied in the form of 0.5 percent zinc sulphate hydrated with lime, which helps in reducing fruit drop and enhancing fruit yield and quality. Boron in the form of borax (600 ppm) enhances fruit setting and reduces fruit cracking.

In acidic soil application of 10-15 kg lime/tree once in 3 years has been found to increase the yield. In general, application of FYM, potassic and phosphoric fertilizers in major lychee growing areas of the country is done during June-July, just after harvesting of the crop. However, in heavy rainfall areas like West Bengal, Uttaranchal, and Uttar Pradesh, manure and fertilizers are applied in the month of September-October just before the end of monsoon. The nitrogen is applied in two equal spilt doses. The first dose is applied after fruit set, in the month of March-April while the remaining half dose is applied immediately after harvesting of the crop. After application of fertilizer, irrigation of the tree is essential to maintain proper soil moisture. The total requirement of nitrogen, phosphorus and potash is applied through basal application. However 2 percent urea spray is practiced once or twice during the period of fruit growth as needed.

Foliar application of zinc sulphate (0.1 percent) is done twice, 10-15 days before flowering for improving sex ratio and to reduce fruit drop. If a deficiency of zinc and magnesium is observed, application of 150-200 g ZnSO 4 and 150-200 g MgSO 4 , respectively per plant during September has been found to be beneficial. Foliar application of 0.1 percent borax, 2-3 times during the period of fruit growth and development of the trees enhances fruit retention, minimizes cracking, improves fruit colour and sweetness, and advances maturity. Other micronutrients like Fe (Ferrous sulphate), Cu (Copper sulphate), Mg (Magnesium sulphate) are applied if deficiency symptoms are observed. Two to three spray in a year is sufficient to maintain the trees in good health.

Foliar application of the plant bio-regulator, NAA (20 ppm) at an interval of 10-15 days during the period of fruit growth and development, twice or thrice, has been found to be useful for minimizing the fruit drop. IAA may be substituted for NAA if the latter is not available. Spraying plain water four to six times in the early morning hours of the day during the advanced stage of fruit growth and development have been found to be highly effective for achieving better growth with minimized fruit cracking.

Monitoring of plant nutrients is done arbitrarily although some farmers get their soil analyzed for pH and nutrients content once in a while. However, it is advocated to use leaf nutrients as diagnostics for monitoring nutrient needs (Kotur and Singh, 1993). Application of fertilizer based on leaf analysis values, though holding promise, is not yet a reality. Babita (Personal Communication) observed that the critical value of nutrients could be used as a guide to determine the nutritional needs, and could economize on fertilizer and provide higher yields of quality fruits.

Irrigation, mulching and water conservation

Lychee being an evergreen plant, the maintenance of optimum soil moisture is critical for growth, development and fruit production. If the rainfall is evenly distributed lychee is grown successfully and supplementary water requirement depends upon cultivar and evaporation demand. Water requirement ranges from 600-800 mm. Investigations carried out to determine the irrigation needs have clearly indicated that irrigation is critical at the fruit development stage to get better yield and quality of fruits. Interestingly, differential management of water in the vegetative phase and reproductive phase is also suggested. To achieve faster growth of the plant no water stress should be permitted, while in the reproductive phase water stress is beneficial at the time of fruit bud differentiation. Light irrigation during summer and winter months and cleaning of the basin is advocated. Irrigation at the intervals of 2-3 days during the initial stage of plant establishment is considered essential. Further, the young plants should be irrigated during dry periods and winter months at intervals of 3-5 days. For young plants mulching with dry leaves or residues in the basin help in better moisture conservation. Experiments conducted at Ranchi indicated that irrigation of plants at alternate day intervals, 6 weeks before harvesting improves fruit retention, encourages better fruit development, and minimizes the cracking, apart from the quality of fruits. Certain physiological disorders like poor sex ratio, poor fruit set, heavy fruit drop and high fruit cracking, besides sunburn of the fruits can be minimized with proper water management. The basin or flood method of irrigation is normally practiced. However, adoption of drip irrigation has been found to be effective in the economic use of water and enhanced growth, especially in an area where water availability is not satisfactory.

Moisture conservation through mulching using dried weeds or black polythene sheet has been found useful. Trials have also been conducted to conserve moisture using farm residues and polythene sheets. Through adoption of mulching, frequency of irrigation is reduced. In a trial conducted at Ranchi mulching with 3 irrigations was effective in reducing cracking and enhancing yield and quality of fruits (Singh, 1986). To check fruit cracking mulching with 3-4 irrigations during fruit growth has been found to be satisfactory.

Filler plant and intercropping

Lychee is a slow growing plant and takes about 15-16 years to develop canopy and cover the area. During the initial period of establishment, the space between the plants can be utilized for planting of filler plants/intercrops. The planting of guava, custard apple, lime/lemon in the centre, between and within the rows of lychee have been found to give additional income in the initial stage of planting without competing with the main crop. Papaya is also planted as filler plant at the spacing of 2.5 x 2.5 m. In between the plants in the initial stage, cowpea, french bean, okra, brinjal or other suitable crops of the regions are grown as intercrops. In the mature lychee orchards, cultivation of partial shade loving plants (ginger, turmeric, elephant foot yam) is practiced successfully, which provides additional income.

Control of pests, diseases and physiological disorders

Lychee plants and fruits are affected by insect pests and diseases, which causes considerable losses, if not managed. Lychee plants as compared to many fruit bearing species are least affected by diseases. A few leaf spot diseases have come to light that are caused by fungal pathogens. No bacterial or viral infections have been reported so far. Powdery mildew ( Oidium spp.), anthracnose or leaf spot ( Botryodiplodia theobormae Pat , Colletotrichum gloeosporioides Penz ) and red rust ( Cephalexros mycoides ) are some diseases which cause some damage to the lychee crop, but severity varies from season to season even in the same locality. Their control measures consist of 1-2 applications of proper fungicides, while for red rust sulphur washes in September-October and February-March is sufficient.

Although about 40 insect and mite pests are reported to affect lychee trees and fruits at different stages of growth, erinose mite, lychee bug and fruit borer are the insect pests of most concern.

Lychee mite ( Aceria litchi ) is a serious pest in all the lychee growing regions in the country. The tiny nymph and adults stick to the under-surface of the leaf and suck the cell sap. Consequently, the young leaf turns yellow to greyish-yellow and a velvety growth develops on lower surfaces, which subsequently turn brown. The affected mature leaf develops continuous to scattered brown patches with curling, twisting and leathery structure, which ultimately result in blister-like gall formations. It spreads fast under favourable conditions and reduces the photosynthesis activity and increases leaf drop. As a result the tree becomes weak, and yield and quality of the fruit is severely affected. The pest is well studied. It is suggested to prune the affected twigs/branches and burn to avoid spread. Two sprays of karathene 0.05 percent at 7-10 days interval during the attack of the insect has been found to effectively control the pest. Application of neem cake has also been found to reduce the incidence of this pest.

In lychee orchards incidence of shoot borer is reported. The caterpillar bore inside the newly growing shoot and feed on inner parts resulting in drying of the twigs. In the case of severe infestation the sap movement is interrupted and the tree ceases to flush. Pruning and burning of affected twigs minimize the infestation.

Bark eating caterpillar and trunk borer

The caterpillar ( Inderbela sp.) bore inside the trunk/main stem. During the night they come out and feed on the bark protected by the large silken webs usually during July-September. The branch ceases growth and the stem becomes weak and may ultimately fall to the ground. The presence of the insect can be known by seeing the excreta and silky web. This pest has become a very serious problem in Bihar state where yield and quality of fruits have been adversely affected. Cleaning of the infested area and plugging holes with petrol, nuvacron or formaline soaked material is advocated.

This pest becomes serious especially in humid conditions at the time of ripening. The small caterpillars bore through the stalk end of the fruit, and feed on the seed and skin. As a result fruits become unfit for consumption. The excreta of the caterpillar is seen near the stalk end of the fruit. High humidity and intermittent rains favour the infestation.

Besides the important pests described above, lychee are often affected by leaf eating caterpillars, leaf miners, bugs and aphids. Birds, bats and squirrels also cause damage to lychee fruits.

Weeds Compete for water and nutrients during the initial year of growth. Depending upon location more than 25 species of weeds are reported to be present in lychee orchards. Inter-culture operation and mulching suppress the weeds. Herbicides, although found effective for the control, are rarely applied. In mature orchards the weed problem is not encountered due to heavy shade and natural mulching by falling leaves.

Fruit cracking is one of the major limiting factors in the cultivation of lychee, especially early cultivars (Singh, 1986). The early varieties are more prone to the problem of fruit cracking in comparison to late cultivars. The low atmospheric humidity, high temperature and hot winds during fruit development and maturity stage favour fruit cracking. Light irrigation to maintain soil moisture and to improve humidity has been found to minimize this problem through maintenance of a better micro-climate. Mulching with farm residues and 3 irrigations significantly reduced the cracking (Singh, 1986) in a trial conducted on the cultivar Shahi. In addition, spraying with either 100 ppm NAA or 0.2 percent borax during the developing stage of the fruits has been found to be highly effective in checking the cracking.

5. HARVESTING OF FRUITS AND YIELDS

Lychee being a non-climacteric fruit requires to be harvested after attaining full maturity on the tree. Studies have been conducted to determine the maturity standard for different cultivars under different agro-climatic conditions. Fruits have a sigmoid pattern of growth. First the pericarp develops, then the seed and aril is formed and the seed turn from green to brown. During maturity acidity declines and TSS increases which corroborate the appearance and colour on the fruit. Thus, the colour of fruit is an important criteria to decide the harvesting stage (Singh and Yadav, 1988). The red pigmentation in lychee is associated with anthocyanin pigments (cyanindin-3-glucoside, cyanindin-3-galactoside, pelargonidin-3-glucoside and pelargonidin-3, 5-diglucozide), which develop better in the direction of good light penetration. Invariably pericarp colour and smoothness of pubicles are the best indicators (Singh and Yadav, 1988). Depending upon the cultivar, 65-80 days are taken for maturity from fruit set.

The fruits are harvested in bunches along with a portion of the branch and a few leaves. At the time of harvesting care is taken to harvest the selected bunch, which has attained the desirable maturity as determined by colour development and taste of the pulp. For distant market fruits are harvested when TSS attains 19° Brix and acidity 0.3 to 0.4 percent. The fruits are harvested early in the morning when temperature and humidity are congenial, to have longer shelf-life of the fruit. At the time of harvest fruits are collected in a manner so that they do not fall on the ground. Use of mechanical tools for harvesting is practiced. The harvesting period is generally May-June, depending upon cultivar and location. However, in the hills of southern India lychee is harvested in November- December.

Changes in the physicochemical characteristics of lychee after anthesis were observed at two locations. Interestingly, the cultivar Rose Scented had similar patterns of growth at both locations, but the maturity date was one month later in comparison with Muzaffarpur. This phenomenon of maturity at two locations provides an opportunity for extended harvest of fruits. Maturity of fruits at Muzaffarpur was one month earlier than Dhaulakuan (H.P)

The yield of lychee varies according to the age of the tree, agro-climatic condition and maintenance of the orchard. Usually about 80-150 kg fruit/tree is obtained from 14-16 year old trees. However, from a fully grown tree a yield of 160-200 kg/tree has also been recorded. Apart from a management practice, bee keeping in lychee orchards has been found to increase the yield of quality fruits by 15-20 percent, since lychee needs cross-pollination. Apis mellifera is the commonly used bee in lychee orchards, which also provide additional income from honey.

Lychee deteriorates very fast after harvest. Pericarp browning is a major post-harvest problem, which renders the fruit unmarketable. Browning is associated with desiccation. Peroxidase activity coupled with ascorbic acid oxidation enhances anthocyanin degradation. Techniques to reduce browning and maintain the red colour and prolonged storage life include sulphur treatment and packaging in perforated plastic bags and storage under cold conditions. Sulphur dioxide (S0 2) fumigation is used as a post-harvest treatment to reduce browning. SO 2 treated fruits have a bleached pericarp which turns uniformly pink in colour after 2-3 days. Fumigated fruits absorb 30-65 percent of applied SO 2. There is increasing concern about the residue of sulphur and the residual limit is only 10 ppm. For sea transportation 600-650g sulphur is recommend for the duration of 50-60 minutes, while for air transport 300-400 g sulphur for 30 minutes are advocated. The Agricultural Produce Export Development Authority (APEDA) has developed a procedure for production of quality lychee. The steps are: production > inspection of farm > harvesting > desolating and sorting > receipt at packhouse > acceptance of produce > sorting and grading > sulphur treatments > packing and cooling > palletization > storage > container loading and transportation.

Aril breakdown or softening of the aril involves a loss of turgidity and translucency where fruits become blunt in taste. The disorder starts near the pericarp and is prevalent at the end of the stem. Post-harvest decay also occurs due to bacteria, yeast and fungi. Lychee browning and fungal contamination is prevented by dipping fruits in hot benomyl. Since this chemical is being restricted from use, alternative methods are desirable. Irradiation of fruit is considered to reduce browning and post-harvest losses. Storage temperature of 2-5°C is considered to extend the shelf-life. Use of perforated polythene bags and storage at 3°C have also been reported to increase shelf-life. Controlled atmosphere storage is considered better for maintenance of the freshness of the fruits. Thus, to have better post-harvest life of fruits, careful harvesting, pre- cooling, transportation in cool van, sulfuring and storing at 2-3°C would be essential.

Processing of lychee is done in different forms. Canning of pulp, aseptic packing and ready to serve lychee juice are common. Dried lychee processing is not in practice. Pulp of lychee is aseptically packed and stored at 2-3°C for preparing lychee juice.

A substantial amount of lychee produced in the country is consumed locally. Lychee, being highly perishable, is available for very short duration. Marketing of fruits is done in different forms. Growers rent their orchards to contractors, who in turn harvest and sell to local markets. Different market chains prevalent are given in Figure 1.

In chains of marketing increased numbers of middlemen reduces the share of growers in the price of produce paid by consumers. Generally, for the domestic market lychee is packed in 10 kg boxes or baskets having a lining of lychee leaves. There has been considerable importance given to the packing of lychee for niche domestic markets. Now lychee is packed in 2-2.5 kg boxes and transported in cool-chain.

In the last few years serious attempts have been made to export lychee from India. Test consignments were initially sent by air and the technology for sea transport has also been perfected. The exportable lychee is packed in 2 to 2.5 kg or 5 to 6 kg boxes after sulphur treatment. Quality standards are managed as per the standard developed by APEDA. The strong cooperative marketing and infrastructure facilities developed are expected to promote marketing of lychee.

7. POTENTIAL FOR LYCHEE PRODUCTION DEVELOPMENT

With increased market base, there is an ample opportunity for increasing the area under lychee as prevailing agro-climatic conditions have not been fully exploited. Extended area under different situations could be exploited for extended harvest. Based on the fruiting behaviour, quality development and area under cultivation, the lychee growing districts could be grouped in a manner to take full advantage of climatic variability. However, to increase production and productivity, concerted efforts would be required for technological support and development of infrastructure. The foothills of the Himalayas free from frost offer good scope for plantation of lychee. Experience has indicated that lychee cultivation can be done up to an altitude of 1,000 m above mean sea level. In these foothills, fruits mature late and ensure the availability of fruits late in the season. Interestingly, the lychee crop in India matures early in comparison to other lychee growing countries and offers better domestic and export markets. Accordingly there is potential for an additional 100,000 hectares to be brought under lychee cultivation. However, to achieve targeted growth in production, strategic planning, including improved production systems and infrastructure for post-harvest management, is needed.

8. CONSTRAINTS IN LYCHEE PRODUCTION DEVELOPMENT

Despite the fact that the lychee is one of the finest fruits and has a growing demand in national and international markets, productivity continues to be low and a gap exists between potential and existing yield. The ratio in yield between the best managed orchards and national productivity ranges between 2 to 4 times at different locations. The probable reasons for low yield are the narrow genetic base of the crop, non-availability of suitable superior cultivars, traditional production systems, poor technological support and incidence of insect pests, coupled with poor post-harvest management. The shortage of genuine planting material coupled with the long juvenile period of lychee are also the constraints. The low female/male flower ratio, premature fruit drop, and fruit cracking due to non scientific water and nutrient management also add to low productivity and production of poor quality fruits.

The lychee tree has luxuriant vegetative growth, which causes problems in harvesting. Thus, canopy management to achieve the required plant architecture is essential. Lack of scientific information on critical stages for flower bud differentiation, and requirements of water and nutrients also significantly reduces the yield. The lychee has a short shelf-life. Practices that can enhance post-harvest life of fruits would be useful to achieve higher productivity.

9. GOVERNMENT POLICIES AND PLANS FOR RESEARCH AND DEVELOPMENT OF LYCHEE

The research support for varietal and production technology improvement is provided through the All India Coordinated Research Project on Sub-tropical Fruits, which has four centres located in lychee growing regions. The Central Horticultural Experimental Station CHES), Ranchi, Jharkhand, RAU, Pusa, Samastipur, Bihar, G.B.Pant University of Agriculture and Technology, Pantnagar, Udhamsingh Nagar, Uttaranchal and BCKVV, Mohitnagar, Nadia, West Bengal are engaged in research. The main thrust of research is on augmentation of germplasm, varietal evaluation, orchard management, propagation studies and development of fruit production technologies for higher yield and improved shelf-life. A network project for improving productivity of lychee has also been initiated. A National Research Centre on Lychee has been started for strategic and basic research on lychee.

The state Governments of Bihar, Jharkhand, Bengal, Tripura, Uttar Pradesh, Chattisgarh, and Uttaranchal also having programmes for the propagation of planting material to meet the requirements. Bihar has special focus on lychee development. The Government of India is implementing a programme on ‘Integrated Development of Fruits’ that includes lychee. Under this programme, support is provided for production of planting material, expansion of area under improved cultivars, rejuvenation of old orchards, transfer of technology, micro-irrigation etc. APEDA is making efforts for improving the export of lychee through the creation of infrastructure and enhancing capabilities.

Lychee, a climate specific, evergreen fruit plant, introduced in the country in the 18 th Century has adapted well to the climate in Eastern India, i.e. Bihar, Jharkhand, West Bengal, Tripura, Uttar Pradesh, Uttaranchal, Chattisgarh, Punjab and Himachal Pradesh. Due to its increasing demand the area under cultivation has increased manifold. However, there is need for improving productivity and also widening the genetic base. Concerted research efforts and effective linkages are essential. Suitable cultivars are needed for various climatic conditions. It is also essential to develop promising lines/hybrids, which have larger fruit size, small/chicken-tongued seeds, tolerance to pericarp splitting, and having various maturity groupings. Suitable agro-techniques particularly for source and sink management, micronutrients, post-harvest technology and effective marketing need due attention. In this context exchange of information among countries would be beneficial. The following points need due consideration:

Lychee has a very narrow genetic base, which needs to be widened through selection of genotypes from the existing population. Target oriented programmes must be launched so that germplasm is conserved and used.

A systematic approach for the description of cultivars is needed. Thus, a lychee descriptor needs to be developed.

Faster multiplication techniques for the production of quality planting material need attention.

There is need to develop propagation technology for faster multiplication of quality plants.

The development of nutrition management to maintain tree health and encourage successful flowering, fruiting and quality in sustainable manner, requires attention.

Monitoring of nutrition in lychee through leaf analysis would be an approach for efficient fertilizer use.

Integrated management of nutrient and water with efficient monitoring mechanisms would improve input use efficiency.

Through effective recycling of residues coupled with organic manure, it is possible to improve soil health. Thus, there is an immense potential for organic production of lychee through effective management.

Integrated management of insect pests and diseases is required to improve productivity and reduce the cost of production.

Infrastructure for post-harvest management requires emphasis to reduce risk.

The lychee product range has to be widened for effective utilization.

Cooperation among lychee growing countries for the exchange of information and cultivars is vital. Starting of a network programme on lychee would boost the production and ensure livelihood security of the people.

Chadha, K.L. 1968. Litchi cultivation in India. Indian Hort., 12:13-16 .

Dass, C.S. and K.R. Choudhary. 1958. Floral biology of Litchi ( Litchi chinesis Sonn .). South Indian Hort., 6:17-22.

Kotur, S.C. and H.P. Singh. 1993. Leaf Sampling technique in Litchi ( Litchi chinesis Sonn) Indian J. Agril. Sci., 63:632-8

Kotur, S.C. and H.P. Singh. 1994. Varietal differences in leaf nutrient composition of litchi ( Litchi chinesis Sonn ). Indian J. Hort., 51:59-62

Kunwar, R. and R. Singh. 1993. Note on nutritional survey of litchi orchards in Doon Valley of Garhwal Hills of Uttar Pradesh. Prog. Hort., 25:164-5.


Why do lychee seeds come in different shapes? - Biology

To a plant, leaves are food producing organs. Leaves "absorb" some of the energy in the sunlight that strikes their surfaces and also take in carbon dioxide from the surrounding air in order to run the metabolic process of photosynthesis. The green color of leaves, in fact, is caused by an abundance of the pigment "chlorophyl" which is the specific chemical agent that acts to capture the sunlight energy needed for photosynthesis. The products of photosynthesis are sugars and polysaccharides. An important "waste product" of photosynthesis is oxygen. To an animal, a leaf may be a food source or a place to live on or under (i.e. a "habitat").

What kinds of leaves do we see on the trees found on the Nature Trail?

The leaves found on the trees of the Nature Trail are either broad and flat (like oak leaves) or needle-shaped (like red pine needles). Both kinds of leaves are photosynthetic organs and both kinds of leaves can serve as food or as habitat for a great variety of other organisms.

Why do tree leaves have different shapes?

The shape of a tree's leaves are a response to the tree species' long term ecological and evolutionary histories. An ecosystem's limiting factors may also modify the finished form and shape of a tree's leaves. Understanding of the "logic" behind the varied forms of leaves is facilitated by a firm grasp of the precise functions a leaf must accomplish.
1. A leaf must "capture" sunlight for photosynthesis (and as it does this it may also absorb a great deal of heat!)
2. A leaf must take in carbon dioxide from the surrounding air via pores (called "stomatae"). This carbon dioxide is also needed for photosynthesis. When these leaf stomatae are open to allow the uptake of carbon dioxide, water from inside the leaf is lost to the atmosphere.
The leaf, then, is affected by these balancing acts: enough sunlight and carbon dioxide to run photosynthesis, but not too much associated heat absorption or water loss.

How does this "balancing act" influence the ultimate expression of a leaf's shape?

Leaves high in the tree canopy receive a great deal of sunlight. These leaves tend to be smaller in size (and, therefore, have reduced light absorptive surface area) and tend also to have complex edges and lobes (which enables them to disperse absorbed heat very rapidly). Leaves in the lower tree canopy are more shaded. These lower canopy leaves tend to be larger (more light absorptive surface area) and tend to have reduced expressions of lobes and edges. These trends may be observed in comparing the leaves of high canopy trees (like oaks) to the leaves of low canopy trees (like dogwoods), or they can also be observed in an individual tree that has leaves in both the upper and lower canopies (the white oak, for example). In the white oak the smaller upper canopy leaves are also noted to allow significant amounts of light to pass through the upper canopy in order to keep the lower leaves supplied with sufficient light to allow their continued photosynthesis.

Needle-shaped leaves have a very low light absorptive surface area. Each needle, then, is not able to capture very much sunlight energy for photosynthesis. Needles also have a very thick, outer cuticle coating and special "pit-like" stomatae designed to prevent excessive water loss. Trees with needle-shaped leaves are especially well suited to site's that have drier soils and to climates in which the careful conservation of water is an important survival strategy. Needle-shaped leaves also differ from broad leaves (in our climate zone anyway) in that needles last for three or four years while broad leaves only "live" for a single growing season. These 'evergreen" needled trees, then, have a great advantage over the "deciduous" broad leafed trees in that the metabolic cost of the leaf's synthesis can be recovered via photosynthesis over several growing seasons. Also, the continuous presence of the needles means that whenever environmental conditions are sufficiently moderate (even in the middle of winter!) the needles can photosynthesize and thus gather energy for the tree! A study in Germany compared energy production in beech trees (which have broad, flat leaves) and Norway spruce trees (which have needles). It was found that the beech trees photosynthesize for 176 days in a year while the Norway spruce photosynthesize 260 days in a year! The bottom energy line was that with this increased time base for photosynthesis, the smaller leafed surface area of the Norway spruce was actually 58% more productive than the beech!

Are the arrangements of leaves on a tree always the same?

There are two basic arrangement patterns of leaves on a tree: "mono-layer" and "multi-layer". In a mono-layer arrangement the leaves are arrayed so that no leaf is above and, therefore, shading any other leaves of the tree. This is the leaf pattern seen in the shade dwelling under story trees like the dogwood. In a multi-layer arrangement there are leaves above and below other leaves on the tree. This is the pattern seen in trees which extend u into the upper stories of a forest canopy. The light-rich upper leaves (as previously mentioned) tend to be smaller and more lobed than the lower. This leaf shape facilitates heat loss and prevents extreme self-shading.

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Lychee

The lychee is native to low elevations of the provinces of Kwangtung and Fukien in southern China, where it flourishes especially along rivers and near the seacoast. It has a long and illustrious history having been praised and pictured in Chinese literature from the earliest known record in 1059 A.D. Cultivation spread over the years through neighboring areas of southeastern Asia and offshore islands. Late in the 17th Century, it was carried to Burma and, 100 years later, to India. It arrived in the West Indies in 1775, was being planted in greenhouses in England and France early in the 19th Century, and Europeans took it to the East Indies. It reached Hawaii in 1873, and Florida in 1883, and was conveyed from Florida to California in 1897. It first fruited at Santa Barbara in 1914. In the 1920's, China's annual crop was 30 million lbs (13.6 million kg). In 1937 (before WW II) the crop of Fukien Province alone was over 35 million lbs (16 million kg). In time, India became second to China in lychee production, total plantings covering about 30,000 acres (12,500 ha). There are also extensive plantings in Pakistan, Bangladesh, Burma, former Indochina, Taiwan, Japan, the Philippines, Queensland, Madagascar, Brazil and South Africa. Lychees are grown mostly in dooryards from northern Queensland to New South Wales, but commercial orchards have been established in the past 20 years, some consisting of 5,000 trees.

Madagascar began experimental refrigerated shipments of lychees to France in 1960. It is recorded that there were 2 trees about 6 years old in Natal, South Africa, in 1875. Others were introduced from Mauritius in 1876. Layers from these latter trees were distributed by the Durban Botanical Gardens and lychee-growing expanded steadily until in 1947 there were 5,000 bearing trees on one estate and 5,000 newly planted on another property, a total of 40,000 in all.

In Hawaii, there are many dooryard trees but commercial plantings are small. The fruit appears on local markets and small quantities are exported to the mainland but the lychee is too undependable to be classed as a crop of serious economic potential there. Rather, it is regarded as a combination ornamental and fruit tree.

There are only a few scattered trees in the West Indies and Central America apart from some groves in Cuba, Honduras and Guatemala. In California, the lychee will grow and fruit only in protected locations and the climate is generally too dry for it. There are a few very old trees and one small commercial grove. In the early 1960's, interest in this crop was renewed and some new plantings were being made on irrigated land.

At first it was believed that the lychee was not well suited to Florida because of the lack of winter dormancy, exposing successive flushes of tender new growth to the occasional periods of low temperature from December to March. The earliest plantings at Sanford and Oviedo were killed by severe freezes. A step forward came with the importation of young lychee trees from Fukien, China, by the Rev. W.M. Brewster between 1903 and 1906. This cultivar, the centuries-old 'Chen-Tze' or 'Royal Chen Purple', renamed 'Brewster' in Florida, from the northern limit of the lychee-growing area in China, withstands light frost and proved to be very successful in the Lake Placid area–the "Ridge" section of Central Florida.

Layered trees were available from Reasoner's Royal Palm Nurseries in the early 1920's, and the Reasoner's and the U.S. Department of Agriculture made many new introductions for trial. But there were no large plantings until an improved method of propagation was developed by Col. William R. Grove who became acquainted with the lychee during military service in the Orient, retired from the Army, made his home at Laurel (14 miles south of Sarasota, Florida) and was encouraged by knowledgeable Prof. G. Weidman Groff, who had spent 20 years at Canton Christian College. Col. Grove made arrangements to air-layer hundreds of branches on some of the old, flourishing 'Brewster' trees in Sebring and Babson Park and thus acquired the stock to establish his lychee grove. He planted the first tree in 1938, and by 1940 was selling lychee plants and promoting the lychee as a commercial crop. Many small orchards were planted from Merritt's Island to Homestead and the Florida Lychee Growers' Association was founded in 1952, especially to organize cooperative marketing. The spelling "lychee" was officially adopted by the association upon the strong recommendation of Professor Groff.

In 1960, over 6,000 lbs (2,720 kg) were shipped to New York, 4,000 lbs (1,814 kg) to California, nearly 6,000 lbs (2,720 kg) to Canada, and 3,900 lbs (1, 769 kg) were consumed in Florida, though this was far from a record year. The commercial lychee crop in Florida has fluctuated with weather conditions, being affected not only by freezes but also by drought and strong winds. Production was greatly reduced in 1959, to a lesser extent in 1963, fell drastically in 1965, reached a high of 50,770 lbs (22,727 kg) in 1970, and a low of 7,200 lbs (3,273 kg) in 1974. Some growers lost up to 70% of their crop because of severe cold in the winter of 1979-80. Of course, there are many bearing trees in home gardens that are not represented in production figures. The fruit from these trees may be merely for household consumption or may be purchased at the site by Chinese grocers or restaurant operators, or sold at roadside stands.

Though the Florida lychee industry is small, mainly because of weather hazards, irregular bearing and labor of hand-harvesting, it has attracted much attention to the crop and has contributed to the dissemination of planting material to other areas of the Western Hemisphere. Escalating land values will probably limit the expansion of lychee plantings in this rapidly developing state. Another limiting factor is that much land suitable for lychee culture is already devoted to citrus groves.

Professor Groff, in his book, The lychee and the lungan, tells us that the production of superior types of lychee is a matter of great family pride and local rivalry in China, where the fruit is esteemed as no other. In 1492, a list of 40 lychee varieties, mostly named for families, was published in the Annals of Fukien. In the Kwang provinces there were 22 types, 30 were listed in the Annals of Kwangtung, and 70 were tallied as varieties of Ling Nam. The Chinese claim that the lychee is highly variable under different cultural and soil conditions. Professor Groff concluded that one could catalog 40 or 50 varieties as recognized in Kwangtung, but there were only 15 distinct, widely-known and commercial varieties grown in that province, half of them marketed in season in the City of Canton. Some of these are classed as "mountain" types the majority are "water types" (grown in low, well-irrigated land). There is a special distinction between the kinds of lychee that leak juice when the skin is broken and those that retain the juice within the flesh. The latter are called "dry- and -clean" and are highly prized. There is much variation in form (round, egg-shaped or heart-shaped), skin color and texture, the fragrance and flavor and even the color, of the flesh and the amount of "rag" in the seed cavity and, of prime importance, the size and form of the seed.

The following are the 15 cultivars recognized by Professor Groff:

'No Mai Tsze' , or 'No mi ts 'z' (glutinous rice) is the leading variety in China large, red, "dry-and-clean" seeds often small and shriveled. It is one of the best for drying, and is late in season. It does best when grafted onto the 'Mountain' lychee.

'Kwa Iuk' or 'Kua lu' (hanging green) is a famous lychee large, red with a green tip and a typical green line "dry-and-clean" of outstanding flavor and fragrance. It was, in olden times, a special fruit for presentation to high officials and other persons in positions of honor. Professor Groff was given a single fruit in a little red box!

'Kwai mi' or 'Kuei Wei', (cinnamon flavor) which came to be called 'Mauritius' is smaller, heart-shaped, with rough red skin tinged with green on the shoulders and usually having a thin line running around the fruit. The seed is small and the flesh very sweet and fragrant. The branches of the tree curve upward at the tips and the leaflets curl inward from the midrib.

'Hsiang li' , or 'Heung lai' (fragrant lychee) is home by a tree with distinctive erect habit having upward-pointing leaves. The fruit is small, very rough and prickly, deep-red, with the smallest seeds of all, and the flesh is of superior flavor and fragrance. It is late in season. Those grown in Sin Hsing are better than those grown in other locations.

'Hsi Chio tsu', or 'Sai kok tsz' (rhinoceros horn) is borne by a large-growing tree. The fruit is large, rough, broad at the base and narrow at the apex has somewhat tough and fibrous, but fragrant, sweet, flesh. It ripens early.

'Hak ip' , or 'Hei yeh', (black leaf) is borne by a densely-branched tree with large, pointed, slightly curled, dark-green leaflets. The fruit is medium-red, sometimes with green tinges, broad-shouldered, with thin, soft skin and the flesh, occasionally pinkish, is crisp and sweet. This is rated as "one of the best 'water' lychees."

'Fei tsu hsiao', or 'Fi tsz siu' (imperial concubine's laugh, or smile) is large, amber-colored, thin-skinned, with very sweet, very fragrant flesh. Seeds vary from large to very small. It ripens early.

'T' ang po' , or 'T' ong pok' (pond embankment) is from a small-leaved tree. The fruit is small, red, rough, with thin, juicy acid flesh and very little rag. It is a very early variety.

'Sheung shu wai' or'Shang hou huai', (President of a Board's embrace) is borne on a small-leaved tree. The fruit is large, rounded, red, with many dark spots. It has sweet flesh with little scent and the seed size is variable. It is rather late in season.

'Ch'u ma lsu', or 'Chu ma lsz' (China grass fiber) has distinctive, lush foliage. The leaves are large, overlapping, with long petioles. The fruits are large with prominent shoulders and rough skin, deep red inside. While very fragrant, the flesh is of inferior flavor and clings to the seed which varies from large to small.

'Ta tsao' , or 'Tai tso' (large crop) is widely grown around Canton somewhat egg-shaped skin rough, bright-red with many small, dense dots flesh firm, crisp, sweet, faintly streaked with yellow near the large seed. The juice leaks when the skin is broken. The fruit ripens early.

'Huai chih', or 'Wai chi' (the Wai River lychee) has medium-sized, blunt leaves. The fruit is round with medium-smooth skin, a rich red outside, pink inside and leaking juice. This is not a high class variety but the most commonly grown, high yielding, and late in season.

'San yueh hung', or 'Sam ut hung' (third month red), also called 'Ma yuen', 'Ma un', 'Tsao kuo', 'Tso kwo', 'Tsao li', or 'Tsoli' (early lychee) is grown along dykes. The branches are brittle and break readily the leaves are long, pointed, and thick. The fruit is very large, with red, thick, tough skin and thick, medium-sweet flesh with much rag. The seeds are long but aborted. This variety is popular mainly because it comes into season very early.

'Pai la li chih', or 'Pak lap lai chi' (white wax lychee), also called 'Po le tzu', or 'Pak lik tsz (white fragrant plant), is large, pink, rough, with pinkish, fibrous, not very sweet flesh and large seeds. It ripens very late, after 'Huai chih'.

'Shan chi', or 'Shan chih' (mountain lychee), also called 'Suan chih', or 'Sun chi' (sour lychee) grows wild in the hills and is often planted as a rootstock for better varieties. The tree is of erect habit with erect twigs and large, pointed, short-petioled leaves. The fruit is bright-red, elongated, very rough, with thin flesh, acid flavor and large seed.

'T'im ngam', or 'T'ien yeh' (sweet cliff) is a common variety of lychee which Professor Groff reported to be quite widely grown in Kwantung, but not really on a commercial basis.

In his book, The Litchi, Dr. Lal Behari Singh wrote that Bihar is the center of lychee culture in India, producing 33 selected varieties classified into 15 groups. His extremely detailed descriptions of the 10 cultivars recommended for large-scale cultivation I have abbreviated (with a few bracketed additions from other sources):

'Early Seedless' , or 'Early Bedana'. Fruit 1 1/3 in (3.4 cm) long, heart-shaped to oval rough, red, with green interspaces skin firm and leathery flesh [ivory] to white, soft, sweet seed shrunken, like a dog's tooth. Of good quality. The tree bears a moderate crop, early in season.

'Rose-scented' . Fruit 1 1/4 in (3.2 cm) long rounded-heart-shaped slightly rough, purplish-rose, slightly firm skin flesh gray-white, soft, very sweet. Seed round-ovate, fully developed. Of good quality. [Tree bears a moderate crop] in midseason.

'Early Large Red' . Fruit slightly more than 1 1/3 in (3.4 cm) long, usually obliquely heart-shaped crimson [to carmine], with green interspaces very rough skin very firm and leathery, adhering slightly to the flesh. Flesh grayish-white, firm, sweet and flavorful. Of very good quality. [Tree is a moderate bearer], early in season.

'Dehra Dun', [or 'Dehra Dhun']. Fruit less than 1 1/2 in (4 cm) long obliquely heart-shaped to conical a blend of red and orange-red skin rough, leathery flesh gray-white, soft, of good, sweet flavor. Seed often shrunken, occasionally very small. Of good quality midseason. [This is grown extensively in Uttar Pradesh and is the most satisfactory lychee in Pakistan.]

'Late Long Red', or 'Muzaffarpur'. Fruit less than 1 1/2 in (4 cm) long usually oblong-conical dark-red with greenish interspaces skin rough, firm and leathery, slightly adhering to the flesh flesh grayish-white, soft, of good, sweet flavor. Seed cylindrical, fully developed. Of good quality. [Tree is a heavy bearer], late in season.

'Pyazi'. Fruit 1 1/3 in (3.4 cm) long oblong-conical to heart-shaped a blend of orange and orange-red, with yellowish-red, not very prominent, tubercles. Skin leathery, adhering flesh gray-white, firm, slightly sweet, with flavor reminiscent of "boiled onion". Seed cylindrical, fully developed. Of poor quality. Early in season.

'Extra Early Green'. Fruit 1 1/4 in (3.2 cm) long mostly heart-shaped, rarely rounded or oblong yellowish-red with green interspaces skin slightly rough, leathery, slightly adhering flesh creamy-white, [firm, of good, slightly acid flavor] seed oblong, cylindrical or flat. Of indifferent quality. Very early in season.

'Kalkattia', ['Calcuttia', or 'Calcutta']. Fruit 1 1/2 in (4 cm) long oblong or lopsided rose-red with darker tubercles skin very rough, leathery, slightly adhering flesh grayish ivory, firm, of very sweet, good flavor. Seed oblong or concave. Of very good quality. [A heavy bearer withstands hot winds]. Very late in season.

'Gulabi'. Fruit 1 1/3 in (3.4 cm) long heart-shaped, oval or oblong pink-red to carmine with orange-red tubercles skin very rough, leathery, non-adherent flesh gray-white, firm, of good subacid flavor seed oblong-cylindrical, fully developed. Of very good quality. Late in season.

'Late Seedless' , or 'Late Bedana'. Fruit less than 1 3/8 in (3.65 cm) long mainly conical, rarely ovate orange-red to carmine with blackish-brown tubercles skin rough, firm, non-adherent flesh creamy-white, soft very sweet, of very good flavor except for slight bitterness near the seed. Seed slightly spindle-shaped, or like a dog's tooth underdeveloped. Of very good quality. [Tree bears heavily. Withstands hot winds.] Late in season.

There are numerous lychee orchards in the submontane region of the Punjab. The leading variety is:

'Panjore common' . Fruit is large, heart-shaped, deep-orange to pink skin is rough, very thin, apt to split. Tree bears heavily and has the longest fruiting season-for an entire month beginning near the end of May. Six other varieties commonly grown there are: 'Rose-scented', 'Bhadwari', 'Seedless No. 1', 'Seedless No. 2', 'Dehra Dun', and 'Kalkattia'.

In South Africa, only one variety is produced commercially. It is the 'Kwai Mi' but it is locally called 'Mauritius' because nearly all of the trees are descendants of those brought in from that island. In South Africa, the fruit is of medium size, nearly round but slightly oval, reddish-brown. Flesh is firm, of good quality and usually contains a medium-sized seed, but certain fruits with broad, flat shoulders and shortened form tend to have "chicken-tongue" seeds.

There have been many other introductions into South Africa from China and India but most failed to survive. In 1928, 16 varieties from India were planted at Lowe's Orchards, Southport, Natal, but the records were lost and they remained unnamed. A Litchi Variety Orchard of 26 cultivars from India, China, Taiwan and elsewhere was established at the Subtropical Horticulture Research Station in Nelspruit. Tentative classifications grouped these into 3 distinct types–'Kwai Mi' ['Mauritius'], 'Hak Ip' (of high quality and small seed but a shy bearer in the Low-veld), and the 'Madras', a heavy bearer of choice fruits, bright-red, very rough, and with large seeds, but very sweet, luscious flesh.

The first lychee introduced into Hawaii was the 'Kwai Mi', as was the second introduction several years later. The high quality of this variety (sometimes locally called 'Charlie Long') caused the lychee to become extremely popular and widely planted. The Hawaiian Agricultural Experiment Station imported 3 'Brewster' trees in 1907, and various efforts were made to bring other types from China but not all survived. A total of 16 varieties became well established in Hawaii, including 'Hak Ip' which has become second to 'Kwai Mi' in importance.

In 1942, the Agricultural Experiment Station set out a collection of 500 seedlings of 'Kwai Mi', 'Hak Ip' and 'Brewster' with a view to selecting the trees showing the best performance. One tree of outstanding character (a seedling of 'Hak Ip') was first designated H.A.E.S. Selection 1-18-3 and was given the name 'Groff' in 1953. It is a consistent bearer, late in season. The fruit is of medium size, dark rose-red with green or yellowish tinges on the apex of each tubercle. The flesh is white and firm there is no leaking juice the flavor is excellent, sweet and subacid most of the fruits have abortive, "chicken-tongue" seeds and, accordingly have 20% more flesh than if the seeds were fully developed.

'No Mai Tsze' has been growing in Hawaii for over 40 years but has produced very few fruits. 'Pat Po Heung' (eight precious fragrances), erroneously called 'Pat Po Hung' (eight precious red), somewhat resembles 'No Mai Tsze' but is smaller the skin is purplish-red, thin and pliable the juice leaks when the skin is broken the flesh is soft, juicy, sweet even when slightly unripe the seed varies from medium to large. The tree is slow-growing and of weak, spreading habit it bears well in Hawaii. Nevertheless, it is not commonly planted.

'Kaimana' , or 'Poamoho', an open-pollinated seedling of 'Hak Ip', developed by Dr. R.A. Hamilton at the Poamoho Experiment Station of the University of Hawaii, was released in 1982. The fruit resembled 'Kwai Mi' but is twice as large, deep-red, of high quality, and the tree is a regular bearer.

'Brewster' is large, conical or wedge-shaped, red, with soft flesh, more acid than that of 'Kwai mi', and the seeds are very often fully formed and large. The leaflets are flat with slightly recurved margins and taper to a sharp point.

There were many other introductions of seeds, seedlings, cuttings or air-layers into the United States, from 1902 to 1924, mostly from China also from India and Hawaii, and a few from Java, Cuba, and Trinidad and these were distributed to experimenters in Florida and California, and some to botanical gardens in other states, and to Cuba, Puerto Rico, Panama, Honduras, Costa Rica and Brazil. Many were killed by cold weather in California and Florida.

In 1908, the United States Department of Agriculture brought in 27 plants of 'Kwai mi'. At the same time, 20 plants of 'Hak Ip' were imported and these were sent to George B. Cellon in Miami in 1918. A tree of the 'Bedana' was introduced from India in 1913. In 1920, Professor Groff obtained seedlings of 'Shan Chi' (mountain lychee) from Kwantung Province, together with air-layers of 'Sheung shu wai', 'No mai ts 'z', and 'T' im ngam' (sweet cliff). The latter was found to bear more regularly than 'Brewster' but exhibited nutritional deficiencies in limestone soil.

Most of the various plants and rooted cuttings from them were distributed for trial the rest were kept in U.S. Department of Agriculture greenhouses in Maryland.

'Bengal' –In 1929, the U.S. Department of Agriculture received a small lychee plant, supposedly a seedling of 'Rose-scented', from Calcutta. It was planted at the Plant Introduction Station in Miami and began bearing in 1940. The fruits resembled 'Brewster' but were more elongated, were home in large clusters, and the flesh was firm, not leaking juice when peeled. All the fruits had fully developed seeds but smaller in proportion to flesh than those of 'Brewster'. The habit of the tree is more spreading than that of 'Brewster' it has larger, more leathery, darker green leave's, and the bark is smoother and paler. The original tree and its air-layered progeny have shown no chlorosis on limestone in contrast to 'Brewster' trees growing nearby.

'Peerless' , believed to be a seedling of 'Brewster', originated at the Royal Palm Nursery at Oneco was transplanted to the T.R. Palmer Estate in Belleair where C.E. Ware noticed from 1936 to 1938 that it bore fruit of larger size, brighter color and higher percentage of abortive seed than 'Brewster'. In 1938, Ware air-layered and removed 200 branches, purchased the tree and moved it to his property in Clearwater. It resumed fruiting in 1940 and annual crops recorded to 1956 showed good productivity-averaging 383.4 lbs (174 kg) per year, and the rate of abortive seeds ranged from 62% to 85%. The 200 air-layers were planted out by Ware in 1942 and began bearing in 1946. Most of the fruits had fully developed seeds but the rate of abortive seeds increased year by year and in 1950 was 61% to 70%. The cultivar was named with the approval of the Florida Lychee Growers Association. Two seedling selections by Col. Grove, 'Yellow Red' and 'Late Globe', Prof. Groff believed to be natural hybrids of 'Brewster' ´ 'Mountain'.

In northern Queensland, 'Kwai Mi' is the earliest cultivar grown, and about 10% of the fruits have "chicken tongue" seeds. 'Brewster' bears in mid-season and is important though the seed is nearly always fully formed and large. 'Hak Ip' is also midseason and large-seeded there. 'Bedana' is grown only in home gardens and the fruits have large seeds unlike the usual "chicken tongue" seeds of the fruits of this cultivar borne in India i

'Wai Chi' is late in season (December), has small, round fruits, basically yellow overlaid with red the seed is small and oval. The tree is very compact with upright branches, and prefers a cooler climate than that of coastal north Queensland where it does not fruit heavily. The leaflets are concave like those of 'Kwai Mi'.

A very similar, perhaps identical, cultivar called 'Hong Kong' is grown in South Queensland. 'No Mai' bears poorly in Queensland and seems better adapted to cooler areas.

There are 3 types of flowers appearing in irregular sequence or, at times, simultaneously, in the lychee inflorescence: a) male b) hermaphrodite, fruiting as female (about 30% of the total) c) hermaphrodite fruiting as male. The latter tend to possess the most viable pollen. Many of the flowers have defective pollen and this fact probably is the main cause of the abortive seeds and also the common problem of shedding of young fruits. The flowers require transfer of pollen by insects.

In India, L.B. Singh recorded 11 species of bees, flies, wasps and other insects as visiting lychee flowers for nectar. But honeybees, mostly Apis cerana indica, A. dorsata and A. florea, constitute 78% of the lychee-pollinating insects and they work the flowers for pollen and nectar from sunrise to sundown. A. cerana is the only hive bee and is essential in commercial orchards for maximum fruit production.

A 6-week survey in Florida revealed 27 species of lychee-flower visitors, representing 6 different insect Orders. Most abundant, morning and afternoon, was the secondary screw-worm fly (Callitroga macellaria), an undesirable pest. Next was the imported honeybee (Apis mellifera) seeking nectar daily but only during the morning and apparently not interested in the pollen. No wild bees were seen on the lychee flowers, though wild bees were found in large numbers collecting pollen in an adjacent fruit-tree planting a few weeks later. Third in order, but not abundant, was the soldier beetle (Chauliognathus marginatus). The rest of the insect visitors were present only in insignificant number. Maintenance of bee hives in Florida lychee groves is necessary to enhance fruit set and development. The fruits mature 2 months after flowering.

In India and Hawaii, there has been some interest in possible cross-breeding of the lychee and pollen storage tests have been conducted. Lychee pollen has remained viable at room temperature for 10 to 30 days in petri dishes for 3 to 5 months in desiccators 15 months at 32° F (0° C) and 25% relative humidity in desiccators and 31 months under deep-freeze, -9.4° F (-23° C). There is considerable variation in the germination rates of pollen from different cultivars. In India, 'Rose Scented' has shown mean viability of 61.99% compared with 42.52% in 'Khattl'.

Groff provided a clear view of the climatic requirements of the lychee. He said that it thrives best in regions "not subject to heavy frost but cool and dry enough in the winter months to provide a period of rest." In China and India, it is grown between 15° and 30° N. "The Canton delta . is crossed by the Tropic of Cancer and is a subtropical area of considerable range in climate. Great fluctuations of temperature are common throughout the fall and winter months. In the winter sudden rises of temperature will at times cause the lychee . to flush forth . new growth. This new growth is seldom subject to a freeze about Canton. On the higher elevations of the mountain regions which are subject to frost the lychee is seldom grown . . . The more hardy mountainous types of the lychee are very sour and those grown near salt water are said to be likewise. The lychee thrives best on the lower plains where the summer months are hot and wet and the winter months are dry and cool."

Heavy frosts will kill young trees but mature trees can withstand light frosts. Cold tolerance of the lychee is intermediate between that of the sweet orange on one hand and mango and avocado on the other. Location, land slope, and proximity to bodies of water can make a great difference in degree of damage by freezing weather. In the severe low temperature crisis during the winter of 1957-58, the effects ranged from minimal to total throughout central and southern Florida. A grove of 12-to 14-year-old trees south of Sanford was killed back nearly to the ground on Merritt Island trees of the same age were virtually undamaged, while a commercial mango planting was totally destroyed. L.B. Singh resists the common belief that the lychee needs winter cold spells that provide periods of temperature between 30° and 40° F (-1.11° and 4.44° C) because it does well in Mauritius where the temperature is never below 40° F (-1.11° C). However, lychee trees in Panama, Jamaica, and other tropical areas set fruit only occasionally or not at all.

Heavy rain or fog during the flowering period is detrimental, as are hot, dry, strong winds which cause shedding of flowers, also splitting of the fruit skin. Splitting occurs, too, during spells of alternating rain and hot, dry periods, especially on the sunny side of the tree. Spraying with Ethephon at 10 ppm reduced splitting in 'Early Large Red' in experiments in Nepal.

The lychee grows well on a wide range of soils. In China it is cultivated in sandy or clayey loam, "river mud", moist sandy clay, and even heavy clay. The pH should be between 6 and 7. If the soil is deficient in lime, this must be added. However, in an early experiment in a greenhouse in Washington, D.C., seedlings planted in acid soil showed superior growth and the roots had many nodules filled with mycorrhizal fungi. This caused some to speculate that inoculation might be desirable. Later, in Florida, profuse nodulation was observed on roots of lychee seedlings that had not been inoculated but merely grown in pots of sphagnum moss and given a well-balanced nutrient solution.

The lychee attains maximum growth and productivity on deep alluvial loam but flourishes in extreme southern Florida on oolitic limestone providing it is put in an adequate hole and irrigated in dry seasons.

The Chinese often plant the lychee on the banks of ponds and streams. In low, wet land, they dig ditches 10 to 15 ft (3-4.5 m) wide and 30 to 40 ft (9-12 m) apart, using the excavated soil to form raised beds on which they plant lychee trees, so that they have perfect drainage but the soil is always moist. Though the lychee has a high water requirement, it cannot stand water-logging. The water table should be at least 4 to 6 ft (1.2-1.8 m) below the surface and the underground water should be moving inasmuch as stagnant water induces root rot. The lychee can stand occasionally brief flooding better than citrus. It will not thrive under saline conditions.

Lychees do not reproduce faithfully from seed, and the choicest have abortive, not viable, seed. Furthermore, lychee seeds remain viable only 4 to 5 days, and seedling trees will not bear until they are 5 to 12, or even 25, years old. For these reasons, seeds are planted mostly for selection and breeding purposes or for rootstock.

Attempts to grow the lychee from cuttings have been generally discouraging, though 80% success has been claimed with spring cuttings in full sun, under constant mist and given weekly liquid nutrients. Ground-layering has been practiced to some extent. In China, air-layering (marcotting, or gootee) is the most popular means of propagation and has been practiced for ages. By their method, a branch of a chosen tree is girdled, allowed to callus for 1 to 2 days and then is enclosed in a ball of sticky mud mixed with chopped straw or dry leaves and wrapped with burlap. With frequent watering, roots develop in the mud and, in about 100 days, the branch is cut off, the ball of earth is increased to about 12 in (30 cm) in width, and the air-layer is kept in a sheltered nursery for a little over a year, then gradually exposed to full sun before it is set out in the orchard. Some air-layers are planted in large clay pots and grown as ornamentals.

The Chinese method of air-layering has many variations. In fact, 92 modifications have been recorded and experimented with in Hawaii. Inarching is also an ancient custom, selected cultivars being joined to 'Mountain' lychee rootstock.

In order to make air-layering less labor-intensive, to eliminate the watering, and also to produce portable, shippable layers, Colonel Grove, after much experimentation, developed the technique of packing the girdle with wet sphagnum moss and soil, wrapping it in moisture-proof clear plastic that permits exchange of air and gasses, and tightly securing it above and below. In about 6 weeks, sufficient roots are formed to permit detaching of the layer, removal of the plastic wrap, and planting in soil in nursery containers. It is possible to air-layer branches up to 4 in (10 cm) thick, and to take 200 to 300 layers from a large tree.

Studies in Mexico have led to the conclusion that, for maximum root formation, branches to be air-layered should not be less than 5/8 in (15 mm) in diameter, and, to avoid undue defoliation of the parent tree, should not exceed 3/4 in (20 mm). The branches, of any age, around the periphery of the canopy and exposed to the sun, make better air-layers with greater root development than branches taken from shaded positions on the tree. The application of growth regulators, at various rates, has shown no significant effect on root development in the Mexican experiments. In India, certain of the various auxins tried stimulated root formation, forced early maturity of the layers, but contributed to high mortality. South African horticulturists believe that tying the branch up so that it is nearly vertical induces vigorous rooting.

The new trees, with about half of the top trimmed off and supported by stakes, are kept in a shadehouse for 6 weeks before setting out. Improvements in Colonel Grove's system later included the use of constant mist in the shadehouse. Also, it was found that birds pecked at the young roots showing through the transparent wrapping, made holes in the plastic and caused dehydration. It became necessary to shield the air-layers with a cylinder of newspaper or aluminum foil. As time went on, some people switched to foil in place of plastic for wrapping the air-layers.

The air-layered trees will fruit in 2 to 5 years after planting, Professor Groff said that a lychee tree is not in its prime until it is 20 to 40 years old will continue bearing a good crop for 100 years or longer. One disadvantage of air-layering is that the resultant trees have weak root systems. In China, a crude method of cleft-grafting has long been employed for special purposes, but, generally speaking, the lychee has been considered very difficult to graft. Bark, tongue, cleft, and side-veneer grafting, also chip-and shield-budding, have been tried by various experimenters in Florida, Hawaii, South Africa and elsewhere with varing degrees of success. The lychee is peculiar in that the entire cambium is active only during the earliest phases of secondary growth. The use of very young rootstocks, only 1/4 in (6 mm) in diameter and wrapping the union with strips of vinyl plastic film, have given good results. A 70% success rate has been achieved in splice-grafting in South Africa. Hardened-off, not terminal, wood of young branches 1/4 in (6 mm) thick is first ringed and the bark-ring removed. After a delay of 21 days, the branch is cut off at the ring, defoliated but leaving the base of each petiole, then a slanting cut is made in the rootstock 1 ft (30 cm) above the soil, at the point where it matches the thickness of the graftwood (scion), and retaining as many leaves as possible. The cut is trimmed to a perfectly smooth surface 1 in (2.5 cm) long the scion is then trimmed to 4 in (10 cm) long, making a slanting cut to match that on the rootstock. The scion should have 2 slightly swollen buds. After joining the scion and the rootstock, the union is wrapped with plastic grafting tape and the scion is completely covered with grafting strips to prevent dehydration. In 6 weeks the buds begin to swell, and the plastic is slit just above the bud to permit sprouting. When the new growth has hardened off, all the grafting tape is removed. The grafting is performed in a moist, warm atmosphere. The grafted plants are maintained in containers for 2 years or more before planting out, and they develop strong taproots.

In India, a more recent development is propagation by stooling, which has been found "simpler, quicker and more economical" there than air-layering. First, air-layers from superior trees are planted 4 ft (1.2 m) apart in "stool beds" where enriched holes have been prepared and left open for 2 weeks. Fertilizer is applied when planting (at the beginning of September) and the air-layers are well established by mid-October and putting out new flushes of growth in November. Fertilizer is applied again in February-March and June-July. Shallow cultivation is performed to keep the plot weed-free. At the end of 2 1/2 years, in mid-February, the plants are cut back to 10 in (25 cm) from the ground. New shoots from the trunk are allowed to grow for 4 months. In mid-June, a ring of bark is removed from all shoots except one on each plant and lanolin paste containing IBA (2,500 ppm) is applied to the upper portion of the ringed area. Ten days later, earth is heaped up to cover 4 to 6 in (10-15 cm) of the stem above the ring. This causes the shoots to root profusely in 2 months. The rooted shoots are separated from the plant and are immediately planted in nursery beds or pots. Those which do not wilt in 3 weeks are judged suitable for setting out in the field. The earth around the parent plants is leveled and the process of fertilization, cultivation, ringing and earthing-up and harvesting of stools is repeated over and over for years until the parent plants have lost their vitality. It is reported that the transplanted shoots have a survival rate of 81-82% as compared with 40% to 50% in air-layers.

Spacing: For a permanent orchard, the trees are best spaced 40 ft (12 m) apart each way. In India, a 30 ft spacing is considered adequate, probably because the drier climate limits the overall growth. Portions of the tree shaded by other trees will not bear fruit. For maximum productivity, there must be full exposure to light on all sides.

In the Cook Islands, the trees are planted on a 40 x 20 ft (12 x 6 m) spacing㫐 trees per acre (134 per ha)–but in the 15th year, the plantation is thinned to 40 x 40 ft (12 x l2 m).

Wind protection: Young trees benefit greatly by wind protection. This can be provided by placing stakes around each small tree and stretching cloth around them as a windscreen. In very windy locations, the entire plantation may be protected by trees planted as windbreaks but these should not be so close as to shade the lychees. The lychee tree is structurally highly wind-resistant, having withstood typhoons, but shelter may be needed to safeguard the crop. During dry, hot months, lychee trees of any age will benefit from overhead sprinkling they are seriously retarded by water stress.

Fertilization: Newly planted trees must be watered but not fertilized beyond the enrichment of the hole well in advance of planting. In China, lychee trees are fertilized only twice a year and only organic material is used, principally night soil, sometimes with the addition of soybean or peanut residue after oil extraction, or mud from canals and fish ponds. There is no great emphasis on fertilization in India. It has been established that a harvest of 1,000 lbs (454.5 kg) removes approximately 3 lbs (1,361 g) K 2 O, 1 lb (454 g) P 2 O 5 , 1 lb (454 g) N, 3/4 lb (340 g) CaO, and 1/2 lb (228 g) MgO from the soil. It is judged, therefore, that applications of potash, phosphate, lime and magnesium should be made to restore these elements.

Fertilizer experiments on fine sand in central Florida have shown that medium rates of N (either sulfate of ammonia or ammonium nitrate), P 2 O 5 , K 2 O, and MgO, together with one application of dolomite limestone at 2 tons/acre (4.8 tons/ha) are beneficial in counteracting chlorosis and promoting growth, flowering and fruit-set and reducing early fruit shedding. Excessive use of nitrogen suppresses growth and interferes with the uptake of other nutrients. If vegetative dormancy is to be encouraged in bearing trees, fertilizer should be withheld in fall and early winter.

In limestone soil, it may be necessary to spread chelated iron 2 or 3 times a year to avoid chlorosis. Zinc deficiency is evidenced by bronzing of the leaves. It is corrected by a foliar spray of 8 lbs (3.5 kg) zinc sulphate and 4 lbs (1.8 kg) hydrated lime in 48 qts (45 liters) of water. Because of the very shallow root system of the lychee, a surface mulch is very beneficial in hot weather.

Pruning: Ordinarily, the tree is not pruned after the judicious shaping of the young plant, because the clipping off of a branch tip with each cluster of fruits is sufficient to promote new growth for the next crop. Severe pruning of old trees may be done to increase fruit size and yield for at least a few years.

Girdling: The Indian farmer may girdle the branches or trunk of his lychee trees in September to enhance flowering and fruiting. Tests on 'Brewster' in Hawaii confirmed the much higher yield obtained from branches girdled in September. Girdling of trees that begin to flush in October and November is ineffective. Similar trials in Florida showed increased yield of trees that had poor crops the previous year, but there was no significant increase in trees that had been heavy bearers. Furthermore, many branches were weakened or killed by girdling. Repeated girdling as a regular practice would probably seriously interfere with overall growth and productivity.

Indian horticulturists warn that girdling in alternate years, or girdling just half of the tree, may be preferable to annual girdling and that, in any case, heavy fertilization and irrigation should precede girdling. Fall spraying of growth inhibitors has not been found to increase yields.

For home use or for local markets, lychees are harvested when fully colored for shipment, when only partly colored. The final swelling of the fruit causes the protuberances on the skin to be less crowded and to slightly flatten out, thus an experienced picker will recognize the stage of full maturity. The fruits are rarely picked singly except for immediate eating out-of-hand, because the stem does not normally detach without breaking the skin and that causes the fruit to spoil quickly. The clusters are usually clipped with a portion of stem and a few leaves attached to prolong freshness. Individual fruits are later clipped from the cluster leaving a stub of stem attached. Harvesting may need to be done every 3 to 4 days over a period of 3-4 weeks. It is never done right after rain, as the wet fruit is very perishable. The lychee tree is not very suitable for the use of ladders. High clusters are usually harvested by metal or bamboo pruning poles. A worker can harvest 55 lbs (25 kg) of fruits per hour.

The yield varies with the cultivar, age, weather, presence of pollinators, and cultural practices. In India, a 5-year-old tree may produce 500 fruits, a 20-year-old tree 4,000 to 5,000 fruits𤪐 to 330 lbs (72.5-149.6 kg). Exceptional trees have borne 1,000 lbs (455 kg) of fruit per year. One tree in Florida has borne 1,200 lbs (544 kg). In China, there are reports of 1,500 lb crops (680 kg). In South Africa, trees 25 years old have averaged 600 lbs (272 kg) each in good years and an average yield per acre is approximately 10,000 lbs annually (roughly equivalent to 10,000 kg per hectare).

Freshly picked lychees keep their color and quality only 3 to 5 days at room temperature. If pre-treated with 0.5% copper sulphate solution and kept in perforated polyethylene bags, they will remain fresh somewhat longer.

Fresh fruits, picked individually by snapping the stems and later de-stemmed during grading, and packed in shallow, ventilated cartons with shredded-paper cushioning, have been successfully shipped by air from Florida to markets throughout the United States and also to Canada. In South Africa, freshly picked lychees have been placed on trays in ventilated sheds, dusted with sulphur and left overnight, and then allowed to "wilt" in lugs for 24 to 48 hours to permit any infested or injured fruits to become conspicuous before grading and packing. It is said that fruits so treated retain their fresh color and are unaffected by fungi or pests for several weeks.

In China and India, lychees are packed in baskets or crates lined with leaves or other cushioning. The clusters or loose fruits are best packed in trays with protective sheets between the layers and no more than 5 single layers or 3 double layers are joined together. The pack should not be too tight. Containers for stacked trays or fruits not so arranged, must be fairly shallow to avoid too much weight and crushing. Spoilage may be retarded by moistening the fruits with a salt solution.

In the Cook Islands, the fruits are removed from the clusters, dipped in Benlate to control fungal growth, dried on racks, then packed in cartons for shipment to New Zealand. South African shippers immerse the fruits for 10 minutes in a suspension of 0.375 dicloran 50% wp plus 0.625 g benomyl 50% wp per liter of water warmed to 125.6º F (52º C). Tests at CSIRO, Div. of Food Research, New South Wales, Australia, in 1982, showed good color retention, retardation of weight loss and fungal spoilage in lychees dipped in hot benomyl 0.05% at 125.6º F (52º C) for two minutes and packed in trays with PVC "skrink" film covering. The chemical treatment had not yet been approved by health authorities.

Lychee clusters shipped to France by air from Madagascar have arrived in fresh condition when packed 13 lbs (6 kg) to the carton and cushioned with leaves of the traveler's tree (Ravenala madagascariensis Sonn.).

Boat shipment requires hydrocooling at the plantation at 32º-35.6º F (0º-2º C), packing in sealed polyethylene bags, storing and conveying to the port at -4º to -13º F (-20º--25º C) and shipping at 32º to 35.6º F (0º-2º C).

In Florida, fresh lychees in sealed, heavy-gauge polyethylene bags keep their color for 7 days in storage or transit at 35º to 50º F (1.67º-10º C). Each bag should contain no more than 15 lbs (6.8 kg) of fruit.

Lychees placed in polyethylene bags with moss, leaves, paper shavings or cotton packing have retained fresh color and quality for 2 weeks in storage at 45º F (7.22º C) for a month at 40º F (4.44º C). At 32º to 35º F(0º-1.67º C) and 85% to 90% relative humidity, untreated lychees, can be stored for 10 weeks the skin will turn brown but the flesh will be virtually in fresh condition but sweeter.

Frozen, peeled or unpeeled, lychees in moisture-vapor-proof containers keep for 2 years.

Plate XXXIII: LYCHEE, Litchi chinensis: dried
Drying of Lychees

Lychees dehydrate naturally. The skin loses its original color, becomes cinnamon-brown, and turns brittle. The flesh turns dark-brown to nearly black as it shrivels and becomes very much like a raisin. The skin of 'Kwai Mi' becomes very tough when dried that of 'Madras' less so. The fruits will dry perfectly if clusters are merely hung in a closed, air-conditioned room.

In China, lychees are preferably dried in the sun on hanging wire trays and brought inside at night and during showers. Some are dried by means of brick stoves during humid weather.

When exports of dried fruits from China to the United States were suspended, India welcomed the opportunity to supply the market. Experimental drying involved preliminary disinfection by immersing the fruits in 0.5% copper sulphate solution for 2 minutes. Sun-drying on coir-mesh trays took 15 days and the results were good except that thin-skinned fruits tended to crack. It was found that shade-drying for 2 days before full exposure to the sun prevented cracking.

Electric-oven drying of single layers arranged in tiers, at 122º to 140º F (50º-65º C), requires only 4 days. Hot-air-blast at 160º F(70º C) dries seedless fruits in 48 hours. Fire-oven and vacuum-oven drying were found unsatisfactory. Florida researchers have demonstrated the feasibility of drying untreated lychees at 120º F (48.8º C) with free-stream air flow rates above 35 CMF/f 2 . Drying at higher temperatures gave the fruits a bitter flavor.

The best quality and light color of flesh instead of dark-brown is achieved by first blanching in boiling water for 5 minutes, immersing in a solution of 2% potassium metabisulphite for 48 hours, and dipping in citric acid prior to drying.

Dried fruits can be stored in tins at room temperature for about a year with no change in texture or flavor.

In most areas where lychees are grown, the most serious foliage pest is the erinose, or leaf-curl, mite, Aceria litchii, which attacks the new growth causing hairy, blister-like galls on the upperside of the leaves, thickening, wrinkling and distorting them, and brown, felt-like wool on the underside. The mite apparently came to Florida on plants from Hawaii in 1953 but has been effectively eradicated. A leaf-webber, Dudua aprobola, attacks the new growth of all lychee trees in the Punjab.

The most destructive enemy of the lychee in China is a stinkbug (Tessaratoma papillosa) with bright-red markings. It sucks the sap from young twigs and they often die at least there is a high rate of fruit-shedding. This pest is combatted by shaking the trees in winter, collecting the bugs and dropping them into kerosene. Without such efforts, it works havoc. A stinkbug (Banasa lenticularis) has been found on lychee foliage in Florida. The leaf-eating false-unicorn caterpillar (Schizura ipomeae), which is parasitized by a tachinid fly (Thorocera floridensis) feeds on the leaves. The foliage is sometimes infested with red spider mites (Paratetranychus hawaiiensis). The citrus aphid (Toxoptera aurantii) preys on flush foliage. Two leaf rollers, Argyroploce leucaspis, and A. aprobola, are active on lychee trees in India. Thrips (Dolicothrips idicus) attack the foliage and Megalurothrips (Taeniothrips) distalis and Lymantria mathura damage the flowers.

A twig-pruner, Hypermallus villosus, has damaged lychee trees in Florida and a twig borer, Proteoteras implicata, has killed twigs of new growth on Florida lychees. The larvae of a native leaf beetle, Exema nodulosa, has been found puncturing and girdling lychee branchlets 1/8 to 1/4 in (3-6 mm) thick. Ambrosia beetles bore into the stems of young trees and fungi enter through their holes. A shoot-borer, Chlumetia transversa, is found on lychee trees all over India. Two bark-boring caterpillars, Indarbela quadrinotata and I. tetraonis, bore rings around the trunk underneath the bark of older trees. The larvae of a small moth, Acrocerops cramerella, eat developing seeds and the pith of young twigs. A small parasitic wasp helps to control this predator, as does the sanitary practice of burning the fallen lychee leaves.

The aphid (Aphis spiraecola) occurs on young plants in shaded nurseries, as does the armored scale, or lychee bark scale, Pseudaulacaspis major, and white peach scale, P. pentagona. The Florida red scale, Chrysomphalus aonidum, has been seen on lychee trees, also the banana-shaped scale, Coccus acutissimus, and green-shield scale, Pulvinaria psidii. The latter is the second most serious pest in Florida. Others are the six-spotted mite, Eotetranychus sexmaculatus, the leaf-footed bug, Leptoglossus phyllopus, and less troublesome creatures such as the several species of Scarabaeidae (related to June bugs) which attack leaves and flower buds.

In South Africa, the parasitic nematode Hemicriconemoides mangiferae and Xiphinema brevicolle cause die-back, decline and ultimately death of lychee trees, sometimes devastating orchards. The root-knot nematode, Meloidogyne javanica, also attacks the lychee in South Africa but is less prevalent.

In Florida, the southern green stinkbug, Nezara viridula, and the larvae of the cotton square borer, Strymon metinus, attack the fruit. Seed-feeding Lepidoptera, especially Cryptophlebia ombrodelta and Lobesia sp. cause much fruit damage and falling in northern Queensland. Carbaryl sprays considerably reduce the losses. In South Africa, a moth, Argyroploce peltastica, lays eggs on the surface of the fruit and the larvae may penetrate weak areas of the skin and infest the flesh. The fruit flies, Ceratites capitata and Pterandrus rosa make minute holes and cracks in the skin and cause internal decay. These pests are so detrimental that growers have adopted the practice of enclosing bunches of clusters (with most of the leaves removed) in bags made of "wet-strength" paper or unbleached calico 6 to 8 weeks before harvest-time. The Caribbean fruit fly, Anastrepha suspensa, has attacked lychee fruits in Florida.

Birds, bats and bees damage ripe fruits on the trees in China and sometimes a stilt house is built beside a choice lychee tree for a watchman to keep guard and ward off these predators, or a large net may be thrown over the tree. In Florida, birds, squirrels, raccoons and rats are prime enemies. Birds have been repelled by hanging on the branches thin metallic ribbons which move, gleam and rattle in the wind. Grasshoppers, crickets, and katydids may, at times, feed heavily on the foliage.

Few diseases have been reported from any lychee-growing locality. The glossy leaves are very resistant to fungi. In Florida, lychee trees are occasionally subject to green scurf, or algal leaf spot (Cephaleuros virescens), leaf blight ( Gleosporium sp.), die-back, caused by Phomopsis sp., and mushroom root rot (Clitocybe tabescens) which is most likely to attack lychee trees planted where oak trees formerly stood. Old oak roots and stumps have been found thoroughly infected with the fungus.

In India, leaf spot caused by Pestalotia pauciseta may be prevalent in December and can be controlled by lime-sulphur sprays. Leaf spots caused by Botryodiplodia theobromae and Colletotrichum gloeosporioides, which begin at the tip of the leaflet, were first noticed in India in 1962.

Lichens and algae commonly grow on the trunks and branches of lychee trees.

The main post-harvest problem is spoilage by the yeast-like organism, which is quick to attack warm, moist fruits. It is important to keep the fruits dry and cool, with good circulation of air. When conditions favor rotting, dusting with fungicide will be necessary.

Fig. 73: Peeled, seeded, lychees (Litchi chinensis) are canned in sirup in the Orient and exported to the United States and other countries.

Lychees are most relished fresh, out-of-hand. Peeled and pitted, they are commonly added to fruit cups and fruit salads. Lychees stuffed with cottage cheese are served as salad topped with dressing and pecans. Or the fruit may be stuffed with a blend of cream cheese and mayonnaise, or stuffed with pecan meats, and garnished with whipped cream. Sliced lychees, congealed in lime gelatin, are served on lettuce with whipped cream or mayonnaise. The fruits may be layered with pistachio ice cream and whipped cream in parfait glasses, as dessert. Halved lychees have been placed on top of ham during the last hour of baking, or grilled on top of steak. Pureed lychees are added to ice cream mix. Sherbet is made by extracting the juice from fresh, seeded lychees and adding it to a mixture of prepared plain gelatin, hot milk, light cream, sugar and a little lemon juice, and freezing.

Peeled, seeded lychees are canned in sugar sirup in India and China and have been exported from China for many years. Browning, or pink discoloration, of the flesh is prevented by the addition of 4% tartaric acid solution, or by using 30º Brix sirup containing 0.1% to 0.15% citric acid to achieve a pH of about 4.5, processing for a maximum of 10 minutes in boiling water, and chilling immediately.

Food Value Per 100 g of Edible Portion*
Fresh Dried
Calories 63-64 277
Moisture 81.9-84.83% 17.90-22.3%
Protein 0.68-1.0 g 2.90-3.8 g
Fat 0.3-0.58 g 0.20-1.2 g
Carbohydrates 13.31-16.4 g 70.7-77.5 g
Fiber 0.23-0.4 g 1.4 g
Ash 0.37-0.5 g 1.5-2.0 g
Calcium 8-10 mg 33 mg
Phosphorus 30-42 mg
Iron 0.4 mg 1.7 mg
Sodium 3 mg 3 mg
Potassium 170 mg 1,100 mg
Thiamine 28 mcg
Nicotinic Acid 0.4 mg
Riboflavin 0.05 mg 0.05 mg
Ascorbic Acid 24-60 mg 42 mg

*According to analyses made in China, India and the Philippines.

The lychee is low in phenols and non-astringent in all stages of maturity.

To a small extent, lychees are also spiced or pickled, or made into sauce, preserves or wine. Lychee jelly has been made from blanched, minced lychees and their accompanying juice, with 1% pectin, and combined phosphoric and citric acid added to enhance the flavor.

The flesh of dried lychees is eaten like raisins. Chinese people enjoy using the dried flesh in their tea as a sweetener in place of sugar.

Whole frozen lychees are thawed in tepid water. They must be consumed very soon, as they discolor and spoil quickly.

In China, great quantities of honey are harvested from hives near lychee trees. Honey from bee colonies in lychee groves in Florida is light amber, of the highest quality, with a rich, delicious flavor like that of the juice which leaks when the fruit is peeled, and the honey does not granulate.

Medicinal Uses: Ingested in moderate amounts, the lychee is said to relieve coughing and to have a beneficial effect on gastralgia, tumors and enlargements of the glands. One stomach-ulcer patient in Florida, has reported that, after eating several fresh lychees he was able to enjoy a large meal that, ordinarily, would have caused great discomfort. Chinese people believe that excessive consumption of raw lychees causes fever and nosebleed. According to legends, ancient devotees have consumed from 300 to 1,000 per day.

In China, the seeds are credited with an analgesic action and they are given in neuralgia and orchitis. A tea of the fruit peel is taken to overcome smallpox eruptions and diarrhea. In India, the seeds are powdered and, because of their astringency, administered in intestinal troubles, and they have the reputation there, as in China, of relieving neuralgic pains. Decoctions of the root, bark and flowers are gargled to alleviate ailments of the throat. Lychee roots have shown activity against one type of tumor in experimental animals in the United States Department of Agriculture/National Cancer Institute Cancer Chemotherapy Screening Program.


Propagation

Lychee trees do not come true from seed, and seedling trees may take 10 or more years to bear fruit. Air layering is the most common method of propagation in Florida (Figure 8). In general, the larger the limb, the easier it is to air layer. Grafting (usually cleft or veneer) and budding onto lychee seedlings or air layers is possible but is not as common as air layering alone this may change as superior rootstocks are identified. Top working is possible although not common and may become more common as superior cultivars are recommended. Air-layered or grafted trees begin to bear fruit in 3 to 5 years.

Seedlings may be useful as rootstocks but are not generally recommended because of genetic variability and vary in their tolerance to different soil conditions (e.g., high-pH, calcareous soil).


Contents

Plant morphology "represents a study of the development, form, and structure of plants, and, by implication, an attempt to interpret these on the basis of similarity of plan and origin". [4] There are four major areas of investigation in plant morphology, and each overlaps with another field of the biological sciences.

First of all, morphology is comparative, meaning that the morphologist examines structures in many different plants of the same or different species, then draws comparisons and formulates ideas about similarities. When structures in different species are believed to exist and develop as a result of common, inherited genetic pathways, those structures are termed homologous. For example, the leaves of pine, oak, and cabbage all look very different, but share certain basic structures and arrangement of parts. The homology of leaves is an easy conclusion to make. The plant morphologist goes further, and discovers that the spines of cactus also share the same basic structure and development as leaves in other plants, and therefore cactus spines are homologous to leaves as well. This aspect of plant morphology overlaps with the study of plant evolution and paleobotany.

Secondly, plant morphology observes both the vegetative (somatic) structures of plants, as well as the reproductive structures. The vegetative structures of vascular plants includes the study of the shoot system, composed of stems and leaves, as well as the root system. The reproductive structures are more varied, and are usually specific to a particular group of plants, such as flowers and seeds, fern sori, and moss capsules. The detailed study of reproductive structures in plants led to the discovery of the alternation of generations found in all plants and most algae. This area of plant morphology overlaps with the study of biodiversity and plant systematics.

Thirdly, plant morphology studies plant structure at a range of scales. At the smallest scales are ultrastructure, the general structural features of cells visible only with the aid of an electron microscope, and cytology, the study of cells using optical microscopy. At this scale, plant morphology overlaps with plant anatomy as a field of study. At the largest scale is the study of plant growth habit, the overall architecture of a plant. The pattern of branching in a tree will vary from species to species, as will the appearance of a plant as a tree, herb, or grass.

Fourthly, plant morphology examines the pattern of development, the process by which structures originate and mature as a plant grows. While animals produce all the body parts they will ever have from early in their life, plants constantly produce new tissues and structures throughout their life. A living plant always has embryonic tissues. The way in which new structures mature as they are produced may be affected by the point in the plant's life when they begin to develop, as well as by the environment to which the structures are exposed. A morphologist studies this process, the causes, and its result. This area of plant morphology overlaps with plant physiology and ecology.

A plant morphologist makes comparisons between structures in many different plants of the same or different species. Making such comparisons between similar structures in different plants tackles the question of why the structures are similar. It is quite likely that similar underlying causes of genetics, physiology, or response to the environment have led to this similarity in appearance. The result of scientific investigation into these causes can lead to one of two insights into the underlying biology:

  1. Homology - the structure is similar between the two species because of shared ancestry and common genetics.
  2. Convergence - the structure is similar between the two species because of independent adaptation to common environmental pressures.

Understanding which characteristics and structures belong to each type is an important part of understanding plant evolution. The evolutionary biologist relies on the plant morphologist to interpret structures, and in turn provides phylogenies of plant relationships that may lead to new morphological insights.

Homology Edit

When structures in different species are believed to exist and develop as a result of common, inherited genetic pathways, those structures are termed homologous. For example, the leaves of pine, oak, and cabbage all look very different, but share certain basic structures and arrangement of parts. The homology of leaves is an easy conclusion to make. The plant morphologist goes further, and discovers that the spines of cactus also share the same basic structure and development as leaves in other plants, and therefore cactus spines are homologous to leaves as well.

Convergence Edit

When structures in different species are believed to exist and develop as a result of common adaptive responses to environmental pressure, those structures are termed convergent. For example, the fronds of Bryopsis plumosa and stems of Asparagus setaceus both have the same feathery branching appearance, even though one is an alga and one is a flowering plant. The similarity in overall structure occurs independently as a result of convergence. The growth form of many cacti and species of Euphorbia is very similar, even though they belong to widely distant families. The similarity results from common solutions to the problem of surviving in a hot, dry environment.

Plant morphology treats both the vegetative structures of plants, as well as the reproductive structures.

The vegetative (somatic) structures of vascular plants include two major organ systems: (1) a shoot system, composed of stems and leaves, and (2) a root system. These two systems are common to nearly all vascular plants, and provide a unifying theme for the study of plant morphology.

By contrast, the reproductive structures are varied, and are usually specific to a particular group of plants. Structures such as flowers and fruits are only found in the angiosperms sori are only found in ferns and seed cones are only found in conifers and other gymnosperms. Reproductive characters are therefore regarded as more useful for the classification of plants than vegetative characters.

Use in identification Edit

Plant biologists use morphological characters of plants which can be compared, measured, counted and described to assess the differences or similarities in plant taxa and use these characters for plant identification, classification and descriptions.

When characters are used in descriptions or for identification they are called diagnostic or key characters which can be either qualitative and quantitative.

  1. Quantitative characters are morphological features that can be counted or measured for example a plant species has flower petals 10–12 mm wide.
  2. Qualitative characters are morphological features such as leaf shape, flower color or pubescence.

Both kinds of characters can be very useful for the identification of plants.

Alternation of generations Edit

The detailed study of reproductive structures in plants led to the discovery of the alternation of generations, found in all plants and most algae, by the German botanist Wilhelm Hofmeister. This discovery is one of the most important made in all of plant morphology, since it provides a common basis for understanding the life cycle of all plants.

Pigmentation in plants Edit

The primary function of pigments in plants is photosynthesis, which uses the green pigment chlorophyll along with several red and yellow pigments that help to capture as much light energy as possible. Pigments are also an important factor in attracting insects to flowers to encourage pollination.

Plant pigments include a variety of different kinds of molecule, including porphyrins, carotenoids, anthocyanins and betalains. All biological pigments selectively absorb certain wavelengths of light while reflecting others. The light that is absorbed may be used by the plant to power chemical reactions, while the reflected wavelengths of light determine the color the pigment will appear to the eye.

Plant development is the process by which structures originate and mature as a plant grows. It is a subject studies in plant anatomy and plant physiology as well as plant morphology.

The process of development in plants is fundamentally different from that seen in vertebrate animals. When an animal embryo begins to develop, it will very early produce all of the body parts that it will ever have in its life. When the animal is born (or hatches from its egg), it has all its body parts and from that point will only grow larger and more mature. By contrast, plants constantly produce new tissues and structures throughout their life from meristems [5] located at the tips of organs, or between mature tissues. Thus, a living plant always has embryonic tissues.

The properties of organization seen in a plant are emergent properties which are more than the sum of the individual parts. "The assembly of these tissues and functions into an integrated multicellular organism yields not only the characteristics of the separate parts and processes but also quite a new set of characteristics which would not have been predictable on the basis of examination of the separate parts." [6] In other words, knowing everything about the molecules in a plant are not enough to predict characteristics of the cells and knowing all the properties of the cells will not predict all the properties of a plant's structure.

Growth Edit

A vascular plant begins from a single celled zygote, formed by fertilisation of an egg cell by a sperm cell. From that point, it begins to divide to form a plant embryo through the process of embryogenesis. As this happens, the resulting cells will organize so that one end becomes the first root, while the other end forms the tip of the shoot. In seed plants, the embryo will develop one or more "seed leaves" (cotyledons). By the end of embryogenesis, the young plant will have all the parts necessary to begin in its life.

Once the embryo germinates from its seed or parent plant, it begins to produce additional organs (leaves, stems, and roots) through the process of organogenesis. New roots grow from root meristems located at the tip of the root, and new stems and leaves grow from shoot meristems located at the tip of the shoot. [7] Branching occurs when small clumps of cells left behind by the meristem, and which have not yet undergone cellular differentiation to form a specialized tissue, begin to grow as the tip of a new root or shoot. Growth from any such meristem at the tip of a root or shoot is termed primary growth and results in the lengthening of that root or shoot. Secondary growth results in widening of a root or shoot from divisions of cells in a cambium. [8]

In addition to growth by cell division, a plant may grow through cell elongation. This occurs when individual cells or groups of cells grow longer. Not all plant cells will grow to the same length. When cells on one side of a stem grow longer and faster than cells on the other side, the stem will bend to the side of the slower growing cells as a result. This directional growth can occur via a plant's response to a particular stimulus, such as light (phototropism), gravity (gravitropism), water, (hydrotropism), and physical contact (thigmotropism).

Plant growth and development are mediated by specific plant hormones and plant growth regulators (PGRs) (Ross et al. 1983). [9] Endogenous hormone levels are influenced by plant age, cold hardiness, dormancy, and other metabolic conditions photoperiod, drought, temperature, and other external environmental conditions and exogenous sources of PGRs, e.g., externally applied and of rhizospheric origin.

Morphological variation Edit

Plants exhibit natural variation in their form and structure. While all organisms vary from individual to individual, plants exhibit an additional type of variation. Within a single individual, parts are repeated which may differ in form and structure from other similar

arts. This variation is most easily seen in the leaves of a plant, though other organs such as stems and flowers may show similar variation. There are three primary causes of this variation: positional effects, environmental effects, and juvenility.

Evolution of plant morphology Edit

Transcription factors and transcriptional regulatory networks play key roles in plant morphogenesis and their evolution. During plant landing, many novel transcription factor families emerged and are preferentially wired into the networks of multicellular development, reproduction, and organ development, contributing to more complex morphogenesis of land plants. [10]

Positional effects Edit

Although plants produce numerous copies of the same organ during their lives, not all copies of a particular organ will be identical. There is variation among the parts of a mature plant resulting from the relative position where the organ is produced. For example, along a new branch the leaves may vary in a consistent pattern along the branch. The form of leaves produced near the base of the branch will differ from leaves produced at the tip of the plant, and this difference is consistent from branch to branch on a given plant and in a given species. This difference persists after the leaves at both ends of the branch have matured, and is not the result of some leaves being younger than others.

Environmental effects Edit

The way in which new structures mature as they are produced may be affected by the point in the plants life when they begin to develop, as well as by the environment to which the structures are exposed. This can be seen in aquatic plants and emergent plants.

Temperature Edit

Temperature has a multiplicity of effects on plants depending on a variety of factors, including the size and condition of the plant and the temperature and duration of exposure. The smaller and more succulent the plant, the greater the susceptibility to damage or death from temperatures that are too high or too low. Temperature affects the rate of biochemical and physiological processes, rates generally (within limits) increasing with temperature. However, the Van’t Hoff relationship for monomolecular reactions (which states that the velocity of a reaction is doubled or trebled by a temperature increase of 10 °C) does not strictly hold for biological processes, especially at low and high temperatures.

When water freezes in plants, the consequences for the plant depend very much on whether the freezing occurs intracellularly (within cells) or outside cells in intercellular (extracellular) spaces. [11] Intracellular freezing usually kills the cell regardless of the hardiness of the plant and its tissues. [12] Intracellular freezing seldom occurs in nature, but moderate rates of decrease in temperature, e.g., 1 °C to 6 °C/hour, cause intercellular ice to form, and this "extraorgan ice" [13] may or may not be lethal, depending on the hardiness of the tissue.

At freezing temperatures, water in the intercellular spaces of plant tissues freezes first, though the water may remain unfrozen until temperatures fall below 7 °C. [11] After the initial formation of ice intercellularly, the cells shrink as water is lost to the segregated ice. The cells undergo freeze-drying, the dehydration being the basic cause of freezing injury.

The rate of cooling has been shown to influence the frost resistance of tissues, [14] but the actual rate of freezing will depend not only on the cooling rate, but also on the degree of supercooling and the properties of the tissue. [15] Sakai (1979a) [14] demonstrated ice segregation in shoot primordia of Alaskan white and black spruces when cooled slowly to 30 °C to -40 °C. These freeze-dehydrated buds survived immersion in liquid nitrogen when slowly rewarmed. Floral primordia responded similarly. Extraorgan freezing in the primordia accounts for the ability of the hardiest of the boreal conifers to survive winters in regions when air temperatures often fall to -50 °C or lower. [13] The hardiness of the winter buds of such conifers is enhanced by the smallness of the buds, by the evolution of faster translocation of water, and an ability to tolerate intensive freeze dehydration. In boreal species of Picea and Pinus, the frost resistance of 1-year-old seedlings is on a par with mature plants, [16] given similar states of dormancy.

Juvenility Edit

The organs and tissues produced by a young plant, such as a seedling, are often different from those that are produced by the same plant when it is older. This phenomenon is known as juvenility or heteroblasty. For example, young trees will produce longer, leaner branches that grow upwards more than the branches they will produce as a fully grown tree. In addition, leaves produced during early growth tend to be larger, thinner, and more irregular than leaves on the adult plant. Specimens of juvenile plants may look so completely different from adult plants of the same species that egg-laying insects do not recognize the plant as food for their young. Differences are seen in rootability and flowering and can be seen in the same mature tree. Juvenile cuttings taken from the base of a tree will form roots much more readily than cuttings originating from the mid to upper crown. Flowering close to the base of a tree is absent or less profuse than flowering in the higher branches especially when a young tree first reaches flowering age. [17]

The transition from early to late growth forms is referred to as 'vegetative phase change', but there is some disagreement about terminology. [18]

Rolf Sattler has revised fundamental concepts of comparative morphology such as the concept of homology. He emphasized that homology should also include partial homology and quantitative homology. [19] [20] This leads to a continuum morphology that demonstrates a continuum between the morphological categories of root, shoot, stem (caulome), leaf (phyllome), and hair (trichome). How intermediates between the categories are best described has been discussed by Bruce K. Kirchoff et al. [21] A recent study conducted by Stalk Institute extracted coordinates corresponding to each plant's base and leaves in 3D space. When plants on the graph were placed according to their actual nutrient travel distances and total branch lengths, the plants fell almost perfectly on the Pareto curve. "This means the way plants grow their architectures also optimizes a very common network design tradeoff. Based on the environment and the species, the plant is selecting different ways to make tradeoffs for those particular environmental conditions." [22]

Honoring Agnes Arber, author of the partial-shoot theory of the leaf, Rutishauser and Isler called the continuum approach Fuzzy Arberian Morphology (FAM). “Fuzzy” refers to fuzzy logic, “Arberian” to Agnes Arber. Rutishauser and Isler emphasized that this approach is not only supported by many morphological data but also by evidence from molecular genetics. [23] More recent evidence from molecular genetics provides further support for continuum morphology. James (2009) concluded that "it is now widely accepted that. radiality [characteristic of most stems] and dorsiventrality [characteristic of leaves] are but extremes of a continuous spectrum. In fact, it is simply the timing of the KNOX gene expression!." [24] Eckardt and Baum (2010) concluded that "it is now generally accepted that compound leaves express both leaf and shoot properties.” [25]

Process morphology describes and analyzes the dynamic continuum of plant form. According to this approach, structures do not have process(es), they are process(es). [26] [27] [28] Thus, the structure/process dichotomy is overcome by "an enlargement of our concept of 'structure' so as to include and recognize that in the living organism it is not merely a question of spatial structure with an 'activity' as something over or against it, but that the concrete organism is a spatio-temporal structure and that this spatio-temporal structure is the activity itself". [29]

For Jeune, Barabé and Lacroix, classical morphology (that is, mainstream morphology, based on a qualitative homology concept implying mutually exclusive categories) and continuum morphology are sub-classes of the more encompassing process morphology (dynamic morphology). [30]

Classical morphology, continuum morphology, and process morphology are highly relevant to plant evolution, especially the field of plant evolutionary biology (plant evo-devo) that tries to integrate plant morphology and plant molecular genetics. [31] In a detailed case study on unusual morphologies, Rutishauser (2016) illustrated and discussed various topics of plant evo-devo such as the fuzziness (continuity) of morphological concepts, the lack of a one-to-one correspondence between structural categories and gene expression, the notion of morphospace, the adaptive value of bauplan features versus patio ludens, physiological adaptations, hopeful monsters and saltational evolution, the significance and limits of developmental robustness, etc. [32]

Whether we like it or not, morphological research is influenced by philosophical assumptions such as either/or logic, fuzzy logic, structure/process dualism or its transcendence. And empirical findings may influence the philosophical assumptions. Thus there are interactions between philosophy and empirical findings. These interactions are the subject of what has been referred to as philosophy of plant morphology. [33]


Unlocking the Secrets of the Pinecone

Introduction
Depending on where you live, this time of year the ground might be covered in snow, ice and, most importantly, pinecones! We see pinecones everywhere during the winter&mdashin wreaths, on trees and in our yards. But did you know that pinecones have a vital job? They keep pine tree seeds safe, and protect them from the freezing temperatures during the winter! To protect their seeds, pinecones can close their &ldquoscales&rdquo tightly, keeping out cold temperatures, winds, ice and even animals that might eat their precious cargo.

In this activity we will observe how pinecones respond to different temperatures by mimicking changes in weather, all from our own kitchens! As an added bonus, after this activity your pinecones will be ready to be added to your house as a holiday decoration or as a reminder of the plants of the season.

Background
Did you know that pinecones can stay on pine trees for more than 10 years before falling to the ground? During that time seeds for new pine trees grow under the scales of the pinecones. The scales protect the seeds from bad weather&mdashand hungry animals. Eventually, however, the seeds need to be released so that they can grow into new trees. To make sure they have the best chance of finding fertile soil and growing into trees, the pinecone scales stay tightly closed when the weather is inhospitable to new seed growth&mdashthat is, when it&rsquos very cold and damp outside. In contrast, when the weather is hot and dry, the seeds will have an easier time finding good soil for growing into trees. In these conditions the pinecone scales will open, allowing seeds to escape and drift away to find new ground to grow into new trees!

As you will observe in this activity, after pinecones fall from the tree they can still open and close we will test the conditions that cause this&mdashall from home!

  • At least three pinecones collected from outside
  • An oven
  • A large clear glass jar or bowl, large enough to hold about a cup of water
  • A measuring tape
  • Cold water
  • A timer
  • Tin foil
  • A piece of paper
  • Pencil or pen
  • A baking tray
  • A spoon or fork
  • Permanent marker
  • An adult helper
  • Ice (optional)

Preparation

  • With the help of an adult, preheat the oven to 250 degrees Fahrenheit.
  • Cover your baking tray with tinfoil.
  • Fill up the glass jar with cold water (including a few pieces of ice if available).
  • Use your permanent marker to label your pinecones. On the first one write the letter &ldquoA.&rdquo On the second pinecone write &ldquoB&rdquo and on the third write &ldquoC.&rdquo
  • On your paper, make three rows. Label the rows A, B and C. Draw six columns. Label the columns &ldquoInitial Length,&rdquo &ldquoInitial Circumference,&rdquo &ldquoCold Water Length,&rdquo &ldquoCold Water Circumference,&rdquo &ldquoFinal Length&rdquo and &ldquoFinal Circumference.&rdquo
  • Use your measuring tape to measure the length of each each pinecone. For each pinecone, write down the length in the column Initial Length. For all measurements in this activity, use centimeters (cm).
  • Use your measuring tape to measure the circumference of each pinecone at its widest point. For each pinecone, write down the circumference in the column Initial Circumference.
  • Place pinecone A on the foil-covered baking tray. With the help of an adult, put the tray in the 250-degree F oven.
  • With the help of an adult, check the pinecone every 10 minutes to make sure it doesn't burn. Are the pinecones changing in any way as they get warmer? What do you notice about them as they get hot?
  • While pinecone A heats up, place pinecone B in the cold water. Use your spoon to hold it underwater. Keep it there for two minutes. What do you notice about the pinecone in the water? Does it sink or float? Why do you think this is true? Do you notice any changes as the pinecone sits under the cold water?
  • Remove the pinecone from the cold water.
  • Use your measuring tape to measure the length of pinecone B. Write down the length in the column Cold Water Length.
  • Use your measuring tape to again measure the circumference of pinecone B at the widest point. Write down its circumference in the column Cold Water Circumference. Compare the length and circumference of pinecone B in each column. Did its length or circumference change after you put it in cold water? If so, what kind of changes did you notice? Did it get larger or smaller? Do you notice any other changes about the pinecone? Does it look different? In what way?
  • After pinecone A has been in the oven for 45 minutes, with the help of an adult, remove it from the oven. Allow it to cool until you can handle it comfortably.
  • Use your measuring tape to measure the length of pinecones A, B and C. Write down their lengths in the column Final Length.
  • Use your measuring tape to measure the circumference of pinecones A, B and C at their widest points. For each pinecone, write down their circumferences in the column Final Circumference.
  • Compare the length and circumference of the pinecones for each column. If you like, you can use math to measure the changes using a few simple equations (and use the same equations to look for changes in length, by substituting length for circumference):
  • Initial Circumference of Pinecone A
  • Hot Circumference of Pinecone A
  • Change caused by heat on Pinecone A
    • Final Circumference of Pinecone A
    • Initial Circumference of Pinecone B
    • Cold Circumference of Pinecone B
    • Change caused by cold on Pinecone B
    • Final Circumference of Pinecone B
    • Initial Circumference of Pinecone C
    • Change caused by control conditions (air) on Pinecone C
    • Final Circumference of Pinecone C

    Observations and results
    In this activity you observed and recorded the effect of different temperature and conditions on the size and appearance of pinecones. You might have noticed that placing pinecone B in the cold water caused its circumference to decrease. In response to cold and damp conditions, pinecone scales close tightly, making a natural shell to protect the seeds inside.

    After taking pinecone A out of the oven you measured all of the pinecones to get their final measurements. When you compared the initial measurement of pinecone A, you should have observed that its circumference increased after being in the hot oven. The increase in the circumferences of the pinecones results from the scales of the pinecones opening up in response to the warmth of the oven. The pinecones think it's a warm summer day, and are ready to release their seeds!

    This activity brought to you in partnership with Science Buddies


    Fungi Cell Structure and Function

    Fungi are unicellular or multicellular thick-cell-walled heterotroph decomposers that eat decaying matter and make tangles of filaments.

    Learning Objectives

    Describe the physical structures associated with fungi

    Key Takeaways

    Key Points

    • Fungal cell walls are rigid and contain complex polysaccharides called chitin (adds structural strength) and glucans.
    • Ergosterol is the steroid molecule in the cell membranes that replaces the cholesterol found in animal cell membranes.
    • Fungi can be unicellular, multicellular, or dimorphic, which is when the fungi is unicellular or multicellular depending on environmental conditions.
    • Fungi in the morphological vegetative stage consist of a tangle of slender, thread-like hyphae, whereas the reproductive stage is usually more obvious.
    • Fungi like to be in a moist and slightly acidic environment they can grow with or without light or oxygen.
    • Fungi are saprophyte heterotrophs in that they use dead or decomposing organic matter as a source of carbon.

    Key Terms

    • glucan: any polysaccharide that is a polymer of glucose
    • ergosterol: the functional equivalent of cholesterol found in cell membranes of fungi and some protists, as well as, the steroid precursor of vitamin D2
    • mycelium: the vegetative part of any fungus, consisting of a mass of branching, threadlike hyphae, often underground
    • hypha: a long, branching, filamentous structure of a fungus that is the main mode of vegetative growth
    • septum: cell wall division between hyphae of a fungus
    • thallus: vegetative body of a fungus
    • saprophyte: any organism that lives on dead organic matter, as certain fungi and bacteria
    • chitin: a complex polysaccharide, a polymer of N-acetylglucosamine, found in the exoskeletons of arthropods and in the cell walls of fungi thought to be responsible for some forms of asthma in humans

    Cell Structure and Function

    Fungi are eukaryotes and have a complex cellular organization. As eukaryotes, fungal cells contain a membrane-bound nucleus where the DNA is wrapped around histone proteins. A few types of fungi have structures comparable to bacterial plasmids (loops of DNA). Fungal cells also contain mitochondria and a complex system of internal membranes, including the endoplasmic reticulum and Golgi apparatus.

    Unlike plant cells, fungal cells do not have chloroplasts or chlorophyll. Many fungi display bright colors arising from other cellular pigments, ranging from red to green to black. The poisonous Amanita muscaria (fly agaric) is recognizable by its bright red cap with white patches. Pigments in fungi are associated with the cell wall. They play a protective role against ultraviolet radiation and can be toxic.

    The poisonous Amanita muscaria: The poisonous Amanita muscaria is native to temperate and boreal regions of North America.

    The rigid layers of fungal cell walls contain complex polysaccharides called chitin and glucans. Chitin, also found in the exoskeleton of insects, gives structural strength to the cell walls of fungi. The wall protects the cell from desiccation and predators. Fungi have plasma membranes similar to other eukaryotes, except that the structure is stabilized by ergosterol: a steroid molecule that replaces the cholesterol found in animal cell membranes. Most members of the kingdom Fungi are nonmotile.

    Growth

    The vegetative body of a fungus is a unicellular or multicellular thallus. Dimorphic fungi can change from the unicellular to multicellular state depending on environmental conditions. Unicellular fungi are generally referred to as yeasts. Saccharomyces cerevisiae (baker’s yeast) and Candida species (the agents of thrush, a common fungal infection) are examples of unicellular fungi.

    Example of a unicellular fungus: Candida albicans is a yeast cell and the agent of candidiasis and thrush. This organism has a similar morphology to coccus bacteria however, yeast is a eukaryotic organism (note the nucleus).

    Most fungi are multicellular organisms. They display two distinct morphological stages: the vegetative and reproductive. The vegetative stage consists of a tangle of slender thread-like structures called hyphae (singular, hypha ), whereas the reproductive stage can be more conspicuous. The mass of hyphae is a mycelium. It can grow on a surface, in soil or decaying material, in a liquid, or even on living tissue. Although individual hyphae must be observed under a microscope, the mycelium of a fungus can be very large, with some species truly being “the fungus humongous.” The giant Armillaria solidipes (honey mushroom) is considered the largest organism on Earth, spreading across more than 2,000 acres of underground soil in eastern Oregon it is estimated to be at least 2,400 years old.

    Example of a mycelium of a fungus: The mycelium of the fungus Neotestudina rosati can be pathogenic to humans. The fungus enters through a cut or scrape and develops a mycetoma, a chronic subcutaneous infection.

    Most fungal hyphae are divided into separate cells by endwalls called septa (singular, septum) ( a, c). In most phyla of fungi, tiny holes in the septa allow for the rapid flow of nutrients and small molecules from cell to cell along the hypha. They are described as perforated septa. The hyphae in bread molds (which belong to the Phylum Zygomycota) are not separated by septa. Instead, they are formed by large cells containing many nuclei, an arrangement described as coenocytic hyphae ( b). Fungi thrive in environments that are moist and slightly acidic they can grow with or without light.

    Division of hyphae into separate cells: Fungal hyphae may be (a) septated or (b) coenocytic (coeno- = “common” -cytic = “cell”) with many nuclei present in a single hypha. A bright field light micrograph of (c) Phialophora richardsiae shows septa that divide the hyphae.

    Nutrition

    Like animals, fungi are heterotrophs: they use complex organic compounds as a source of carbon, rather than fix carbon dioxide from the atmosphere as do some bacteria and most plants. In addition, fungi do not fix nitrogen from the atmosphere. Like animals, they must obtain it from their diet. However, unlike most animals, which ingest food and then digest it internally in specialized organs, fungi perform these steps in the reverse order: digestion precedes ingestion. First, exoenzymes are transported out of the hyphae, where they process nutrients in the environment. Then, the smaller molecules produced by this external digestion are absorbed through the large surface area of the mycelium. As with animal cells, the polysaccharide of storage is glycogen rather than the starch found in plants.

    Fungi are mostly saprobes (saprophyte is an equivalent term): organisms that derive nutrients from decaying organic matter. They obtain their nutrients from dead or decomposing organic matter, mainly plant material. Fungal exoenzymes are able to break down insoluble polysaccharides, such as the cellulose and lignin of dead wood, into readily-absorbable glucose molecules. The carbon, nitrogen, and other elements are thus released into the environment. Because of their varied metabolic pathways, fungi fulfill an important ecological role and are being investigated as potential tools in bioremediation.

    Some fungi are parasitic, infecting either plants or animals. Smut and Dutch elm disease affect plants, whereas athlete’s foot and candidiasis (thrush) are medically important fungal infections in humans.


    Section Summary

    Angiosperms are the dominant form of plant life in most terrestrial ecosystems, comprising about 90 percent of all plant species. Most crops and ornamental plants are angiosperms. Their success comes from two innovative structures that protect reproduction from variability in the environment: the flower and the fruit. Flowers were derived from modified leaves. The main parts of a flower are the sepals and petals, which protect the reproductive parts: the stamens and the carpels. The stamens produce the male gametes in pollen grains. The carpels contain the female gametes (the eggs inside the ovules), which are within the ovary of a carpel. The walls of the ovary thicken after fertilization, ripening into fruit that ensures dispersal by wind, water, or animals.

    The angiosperm life cycle is dominated by the sporophyte stage. Double fertilization is an event unique to angiosperms. One sperm in the pollen fertilizes the egg, forming a diploid zygote, while the other combines with the two polar nuclei, forming a triploid cell that develops into a food storage tissue called the endosperm. Flowering plants are divided into two main groups, the monocots and eudicots, according to the number of cotyledons in the seedlings. Basal angiosperms belong to an older lineage than monocots and eudicots.


    Difference Between Monocot and Dicot

    Alternative Names

    Monocot: Monocot is called monocotyledon.

    Dicot: Dicot is called dicotyledon.

    Growth Form

    Monocot: Monocots are mostly herbaceous. Some are occasionally arboraceous.

    Dicot: Dicots are either herbaceous or arboraceous.

    Embryo

    Monocot: The embryo of the monocot contains only one cotyledon.

    Dicot: The embryo of the dicot contains two cotyledons.

    Endosperm

    Monocot: Monocot contains a large endosperm inside the seed, feeding the embryo plant.

    Dicot: Dicot contains a tiny endosperm inside the seed.

    Seed Germination

    Monocot: Monocot produces a single leaf, which is long and narrow during the germination of the seed.

    Dicot: Dicot produces two leaves, which are in a different shape to the true leaf.

    Shape of the Leaf

    Monocot: Monocot usually contains long and narrow leaves.

    Dicot: Dicot usually contains wider leaves, but their shapes are highly varied depending on the species.

    Leaf Veins

    Monocot: Monocot contains a parallel venation system.

    Dicot: Dicot contains a reticulate venation system.

    Stems

    Monocot: The stem of the monocot is unbranched and fleshy.

    Dicot: The stem of the dicot is branched and hard.

    Significance in the Stem

    Monocot: The stem of the monocot is always protected from leaves, forming a protective sheath

    Dicot: The stem of the dicot grows wider in each year.

    Vascular Bundles

    Monocot: Monocot contains scattered vascular bundles all over the ground parenchyma.

    Dicot: Primary vascular bundles form a ring in the stem.

    Cambium

    Monocot: Monocot does not contain a cambium.

    Dicot: Dicot contains a cambium between xylem and phloem.

    Stem Differentiation

    Monocot: Monocot lacks differentiation of the stem into cortex and stele.

    Dicot: Dicot consists of the stem differentiation into cortex and stele.

    Roots

    Monocot: Monocot contains a fibrous root system.

    Dicot: Dicot contains roots, growing from the main taproot.

    Flowers

    Monocot: Parts of the flower in monocot is trimerous.

    Dicot: Parts of the flower in dicot are either tetramerous and pentamerous.

    Pollen

    Monocot: Monocot pollen is monocolpate or contains a single aperture.

    Dicot: Dicot pollen is tricolpate.

    Seed Germination

    Monocot: Seed germination of monocot is hypogeal.

    Dicot: Seed germination of dicot is either hypogeal or epigeal.

    Examples

    Monocot: Grasses, cereal grains, palm, and banana are the examples of monocots.

    Dicot: Legumes, tomato, and oak are the examples of dicots.

    Conclusion

    Monocot and dicot are two types of flowering plants. The seed of the monocot produces a single embryo leaf while in germination. In contrast, dicot produces two embryo leaves, which are fatter and in different shapes compared to the true leaves. Monocot contains an unbranched stem while the stem of the dicot is branched and grows wider in each year by the process called secondary growth. Vascular bundles are scattered all over the stem in monocot whereas they are arranged into a ring in the dicot. Monocot contains a fleshy, fibrous roots and dicot contains roots, growing from the main taproot. Leaves of the monocot are usually thin and long. Leaves of the dicot contain a variety of shapes, but generally they are round in shape. Flowers are trimerous in the monocot and they are tetramerous and pentamerous in the dicot. However, the main difference between monocot and dicot is in the number of embryo leaves found in the seed.

    Reference:
    1. “Monocots versus Dicots.” Monocots vs. Dicots. N.p., n.d. Web. 30 Apr. 2017.
    2. Wise, Nicole. “The Science Behind Holganix: Monocots vs Dicots: What You Need To Know.” HOLGANIX The Natural Green Solutio. N.p., n.d. Web. 30 Apr. 2017.
    3. Monocots and Dicots. N.p., n.d. Web. 30 Apr. 2017.

    Image Courtesy:
    1. “Monocot vs dicot Pengo” By w:User:Pengo (CC BY-SA 3.0) via Commons Wikimedia
    2. “Tradescantia pallida flower (CC BY-SA 3.0) via Commons Wikimedia
    3. “Young castor bean plant showing prominent cotyledons” By Rickjpelleg assumed. Own work assumed (based on copyright claims) ( CC BY-SA 2.5) via Commons Wikimedia
    4. “Figure 30 02 06” By CNX OpenStax –(CC BY 4.0) via Commons Wikimedia


    Watch the video: Fruit Oxford Read and Discover Level One:: English Reading Books:: English Audiobooks (December 2021).