Effects of Temperature and Humidity on Lychee (Litchi chinensis Sonn.) Pollen Germination during Anther Dehiscence

抄録

We determined the temperature and humidity conditions during flowering that result in high germination of lychee pollen. Staminate flowers were gathered before anther dehiscence from the South Chinese cultivars ‘Tai So,’ ‘Souey Tung,’ Floridian ‘Bengal,’ and Thai ‘Chakrapat,’ and then incubated for 24 h at various temperature (15–30°C) and relative humidity [RH] (10–75%) combinations. After incubation, the percentage of dehisced anthers was recorded, and then pollen germination was tested. In all cultivars, dehiscence increased at higher temperature or lower humidity. The dehiscence exceeded 90% within 24 h at ≥20°C and RH <60%, except for ‘Souey Tung,’ for which it was generally below 80%. Germination of ‘Bengal’ was highest (≈50%) when the anthers dehisced at 20°C and ≈50% RH, and tended to decrease at higher and lower temperatures. The germination tended to decrease as humidity increased, and this tendency was remarkable at ≥25°C. ‘Chakrapat’ germination was also highest (≈60%) at 20°C and ≈50% RH. ‘Chakrapat’ germinated relatively well at 30°C. Relative humidity >30% affected germination slightly. Similarly, ‘Souey Tung’ and ‘Tai So’ had the highest germination (≈35% and ≈30%, respectively) at 20°C and ≈50% RH, although the germination was low. Similar to ‘Chakrapat,’ ‘ Tai So’ germination decreased slightly at higher temperatures, and was affected little by RH >30%. Pollen-tube elongation was also best at 20°C and ≈50% RH, and tended to decrease at higher temperatures or lower humidity. The optimal temperature/humidity conditions for lychee anther dehiscence were 20°C/≈50% RH, regardless of the cultivar.