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Sukhvibul N.,Chiang Rai Horticultural Research Center | Dasananda M.,Chiang Rai Horticultural Research Center
Acta Horticulturae

Pollen morphology and factors affecting in vitro pollen germination of four commercial litchi cultivars, 'Hong Huai', 'O Hia', 'Kim Cheng' and 'C hakkraphat' were studied at Chiang Rai Horticultural Research Center, Thailand. The pollen was germinated in li×uid medium by using a hanging drop techni×ue in the controlled temperature incubator. The litchi pollen was oblong when dehiscenced, becoming triangular or sometimes rectangular after germination in the li×uid medium. The pollen was binucleate and an average length was 27-28 μm depending on cultivars. There was no difference in germination percentage of 'Hong Huai' pollen incubated in either the presence of light or the darkness at 25?C for 24 hours. There was no significant difference in pollen germination between 'Hong Huai' and 'Chakkraphat' at any incubation periods in the dark at 25?C for 3-24 hours. Average germination percentage of both cultivars sharply increased to 69.2% when the incubation period was prolonged to 3-12 hours. Extending the duration of incubation beyond 18 and 24 hours, germination slowly increased to 87.4 and 89.0%, respectively. In this study, as temperatures increased there was a trend for the pollen germination of all cultivars to increase. Averaged over the four cultivars, 2.0% of pollen germinated at 10?C, this increased to 14.7, 49.6, 60.1 and 63.9% when the incubation temperature was increased to 15, 20, 25 and 30?C, respectively. Raising the incubation temperature to 35?C resulted in decreased germination to 59.8%. The best temperature of pollen germination for all four litchi cultivars was between 25 and 35?C. Source

Sukhvibul N.,Chiang Rai Horticultural Research Center | Dasananda M.,Chiang Rai Horticultural Research Center | Vorapitiruangsri S.,Chiang Rai Horticultural Research Center
Acta Horticulturae

Developments of leaf, inflorescence, floral and fruit of 'Khom', 'Nakhon Phanom 1', 'Phan Thip', 'Kalok Bai Khing' and 'Hong Huai' litchi cultivars were studied in Chiang Rai and Pha Yao provinces in 2009. First leaf flushing emerged in June and the second flushing emerged in August. Young folded leaf fully expanded within 20.3 days and further developed to be fully mature leaf within 18.7 days. Chlorophyll fluorescence (Fv/Fm ratio) and chlorophyll content in leaves increased as the leaves age. Fv/Fm ratio of 'Hong Huai' leaves tended to be higher than 0.7000 and changed very little during the growth cycle. Fv/Fm ratio in leaves of lowland cultivars declined to 0.6850-0.7540 during winter period. Chlorophyll content in leaves of all cultivars changed little during annual growth and pre-flowering period which seemed to be not important for floral differentiation. Similarly, contents of total non-structural carbohydrate and total nitrogen in leaves and shoots of all cultivars seemed to be no constant changes. Inflorescences of lowland cultivars emerged in late of December or 15-20 days earlier than 'Hong Huai' cultivar. Inflorescences reached the maximum length within 38 to 45 days after emergence. Each inflorescence produced both male and hermaphrodite as female or male flowers but the sex ratio differed among cultivars. Number of flower, flower size, blooming pattern and pollen viability also varied depending on cultivars. After fruit setting, the peel and seed differentiated within 8 days and the aril appeared in about 20 days later. Most of the massive abscission of fruitlets occurred during 1 to 20 days after pollination. The fruit matured about 68 days after setting. The development of leaves, inflorescences and fruits of all cultivars followed the sigmoidal curve of Y=a+b/(1+ex(-(x-c)/d)) which were different in cultivars. Source

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