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Hannes Robbertse, Jaco Fivaz, and Chris Menzel

The architecture of the lychee tree and the structure of the inflorescence are described according to the terminology of Hallè et al. and Weberling. The lychee tree has rhythmic modular growth and the inflorescence is a heterocladic pleiothyrsoid. Additional paracladia may develop from a second serial bud below the first-order paracladia. Male and female flowers are borne at variable positions on the dichasia. The relation between the position and gender of the flowers on the partial inflorescences (dichasia) varied with cultivar and time.

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Raphael A. Stern and Shmuel Gazit

The lychee (Litchi chinensis Sonn.) has two types of pollen-releasing flowers—M1 and M2. We compared the morphology and viability of these two pollen types, mainly for the two commercial cultivars in Israel: `Mauritius' and `Floridian'. Observation by scanning electron microscope did not reveal any consistent morphological differences between the two pollen types. However, M2 pollen was found to have a consistent and significant advantage over M1 pollen in in vitro germination tests. M2 pollen from `Mauritius', `Floridian', `No Mai Chee', `Wai Chee', and `Early Large Red' had a much higher germination rate at 15, 20, 25, 30, and 35 °C than M1 pollen from those same cultivars. The optimal incubation temperature for in vitro pollen germination was 30 °C for M2 pollen of all five cultivars studied; adequate germination rates were also found at 35 and 25 °C. The optimal temperature for M1 pollen germination was also 30 °C for `Mauritius' and `No Mai Chee', but was not well defined for the other three cultivars. No pronounced advantage of M2 pollen-tube growth could be discerned 48 h after hand pollination. However, final fruit set was consistently and significantly higher after hand pollination with M2 pollen, relative to M1 pollen. Hot (32/27 °C) and warm (27/22 °C) regimes during flower development had a pronounced detrimental effect on pollen viability compared to a cool (22/17 °C) regime. `Floridian' was much more susceptible than `Mauritius' in this respect.

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Raymond G. McGuire

I thank Everton Bather for his technical assistance throughout these experiments and the Lychee Growers' Association of South Florida for its donation of fruits used in these studies. Mention of a trade name does not constitute a

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Ricardo Goenaga, David Jenkins, and Angel Marrero

Lychee belongs to the Sapindaceae family and is native to southern China. The crop is grown commercially from latitude 17° to 32° and is usually found at low elevation in the subtropics and from 300 to 600 m in tropical locations ( Menzel and

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Raphael A. Stern and Shmuel Gazit

Pollination of lychee (Litchi chinensis Sonn.) by the honeybee was studied in Israel's two commercial cultivars, `Mauritius' and `Floridian'. Pollination rate, which was determined in a mixed `Mauritius' and `Floridian' plot, followed a consistent pattern: it was low at the first male (M,) `Mauritius' bloom and reached a high value only when the pseudohermaphroditic (M2) `Mauritius' bloom started. Pollen density on bees collected from `Mauritius' inflorescences was very low during the M, bloom and increased to very high values during the M2 bloom. These results indicate that the `Mauritius' M, bloom does not play an important role as a source of pollen for pollination. Pronounced, significant, and consistent differences in nectar volume per flower and sugar concentration in the nectar were found between M1, M2, and female (F) `Mauritius' flowers. Values were very high in F flowers, medium in M2 flowers, and low in M, flowers. Accordingly, the density of bees found on inflorescences was high during the F bloom, intermediate during the M2 bloom, and low during the M1 bloom. The positive correlation between bee density and sugar concentration in the nectar was highly significant for M2 and F `Mauritius' flowers. The nectar contained three sugars: glucose (43%), fructose (39%), and sucrose (18 %). This ratio was the same in nectar from M1, M2, and F `Mauritius' flowers.

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Ashish K. Pathak, Sudhir P. Singh, and Rakesh Tuli

Lychee is a subtropical evergreen fruit tree of family Sapindaceae (soapberry) and subfamily Nepheleae. The edible portion (aril) of the non-climacteric lychee fruit has a sweet and acidic taste, which makes it delicious and popular. The commercial

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C. Degani, A. Beiles, R. El-Batsri, M. Goren, and S. Gazit

Leaf isozyme banding patterns were studied in 30 cultivars and selections of lychee (Litchi Chinensis Sonn.) by means of starch gel electrophoresis. Polymorphism in aconitase, aspartate aminotransferase, isocitrate dehydrogenase, phosphoglucomutase, shikimate dehydrogenase, superoxide dismutase and triosephosphate isomerase is demonstrated for the first time and observations are extended for the previously described polymorphism in phosphoglucose isomerase. In this study we found five groups of cultivars with identical electrophoretic genotypes. The 18 different cultivars were clustered by the UPGMA method into two large clusters and three pairs of similar cultivars. Three cultivars were relatively separate from the clusters. This study shows that isozyme polymorphism is a prevalent phenomenon in lychee, and that isozymes can provide useful genetic markers for lychee cultivar identification and parental analysis.

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S.J.R. Underhill and C. Critchley

Mature lychee (Litchi chinensis Sonn.) fruit were heat-treated at 60C for 10 min to study heat-induced pericarp browning. Polyphenol oxidase (EC 1.10.3.2) activity of the pericarp increased immediately, corresponding with rapid anthocyanin degradation, Tissue browning was observed 2 min after heating, with pigmentation distributed uniformly throughout the pericarp. The distribution of brown pigments was different than the highly localized browning observed under ambient desiccation. Although both ambient and heat-induced pericarp browning are visually similar, the anatomical distribution of brown pigmentation is quite distinct. The distribution of brown pigmentation was not consistent with anthocyanin localization. Following ambient desiccation, the mesocarp became colorless even though this represented the greatest concentration of pigment. Browning caused by heating may result from nonselective degradation of a range of compounds, including anthocyanin.

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Weixin Chen

Lychee is a well-known subtropical fruit, much appreciated for its attractive red peel and excellent taste, but the fruit is very prone to postharvest peel browning and decay. China is the world leader in both acreage and yield of lychee production. Extensive research has been conducted to extend the fruit quality and shelf life. The talk presents a general review of the current research on postharvest physiology and shelf life preservation technologies of lychee in China.

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Thomas E. Marler and Leah E. Willis

`Mauritius' lychee (Litchi chinensis Sonn.) trees were planted in root observation chambers in July 1990 to determine the pattern of root and stem extension growth during 12 months. Root and stem lengths were measured at intervals ranging from 7 to 18 days from Aug. 1990 until Aug. 1991. During each period of active canopy growth, up to six stem tips were tagged and measured. Root growth was determined by measuring tracings of the extension of each root in a visible plane of the glass wall of the observation chambers. Stem growth was cyclic, with distinct periods of rapid extension followed by periods with no extension. In contrast, root growth was fairly continuous with only three periods of no visible root extension. Mean absolute extension rates were higher for stems than for roots. There were no consistent relationships between the timing of root and stem extension growth.