Morphology and Factors Affecting Germination of Litchi Pollen

Abstract

Pollen morphology and factors affecting in vitro pollen germination of four commercial litchi cultivars, Hong Huay, O Hia, Kim Cheng and Jakapad, were studied at Chiang Rai Horticultural Research Center, Thailand. The pollen was germinated in liquid medium by using a hanging drop technique in the controlled temperature incubator. The litchi pollen was oblong when dehiscenced, becoming triangular or sometimes rectangular after germination in the liquid medium. The pollen was binucleate and an average length was 27-28 m depending on cultivars. There was no difference in germination percentage of 'Hong Huay' 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 Huay' and 'Jakapad' 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.