To elucidate the causes of high-temperature stress inducing rice floret infertility, the present study analyzed the effects of high-temperature stresses on pollen release related traits including pollen grain swelling, anther dehiscence, pollen grain residue in anther and pollen grain deposition on the stigma of the differential genotypes Indica at anthesis.

Indica germplasms were sown in batches and cultivated in the Nanchang region, Jiangxi Province, China. The rice plants flowering at natural high-temperature environments on early August with 36.5-37.8 ℃ canopy temperature was used as treatments, and the rice plants flowering at suitable environments on middle September with 30.8-32.5 ℃ canopy temperature were used as controls. The pollen release related traits, such as pollen grain swelling, anther dehiscence, pollen grain residue in anther and pollen grain deposition on the stigma from treatments and controls, were detected and analyzed.

After flowering under high-temperature stress, the rice germplasms Jiangxijiansimiao, Yuexiangzhan and Huangguangyouzhan show high-temperature tolerant at anthesis, and the floret fertility rates are 91.6%, 89.2% and 87.9%, respectively; while the germplasms Zhenfu, Yuzhenxiang, IR64 and Miyang46 show high-temperature sensitive at anthesis, and the floret fertility rates are just 55.2%, 60.3%, 61.1% and 73.2%, which are very significantly or significantly lower than that of its corresponding controls. Under high-temperature environments, the pollen grain swelling rates for the high-temperature sensitive germplasms Zhenfu, Yuzhenxiang, IR64 and Miyang46 are just 1.99%, 1.16%, 1.12% and 2.70%, which are very significant smaller than that of its corresponding controls; while the pollen grain swelling rates of the other germplasms show no significant difference between treatment and its corresponding control. Under high-temperature environments, the rates of anther dehiscence length in total anther length for the high-temperature sensitive germplasms Zhenfu, Yuzhenxiang, IR64 and Miyang46 are respective 66.0%, 45.4%, 48.7% and 63.6%, which are very significantly or significantly shorter than that of the corresponding controls, and the pollen grain residue are obvious more than that of the corresponding controls; while the anther dehiscence length rates and the pollen grain residue from the other germplasms show no significant difference between treatments and controls. After flowering under high-temperature environments, the average pollen grain number deposited on one stigma of the sensitive germplasms were about 20, which were significant less than that of the controls; while the average pollen grain number deposited on one stigma of the other rice germplasms show no significant difference between treatments and controls.

The high-temperature stresses inhibit the pollen grain swelling, effect the anther normal dehiscence, increase the pollen viscidity to impede the pollen grain releasing from anther and decrease the pollen grain number scattering on the stigma, inducing rice floret infertility and decreasing the seed set.