Percentage of dehisced thecae and length of dehiscence control pollination stability of rice cultivars at high temperatures.

Global warming may reduce rice yield through poor pollination caused by high temperatures at flowering. The dominant parameter controlling the pollination stability in rice cultivars at high temperatures was studied. We examined the effects of a high daytime temperature (35.0 degrees C, 37.5 degrees C, 40.0 degrees C) and its duration (1, 3, 5 days) on the percentage of dehisced thecae, the length of dehiscence in the basal part of the theca for pollen dispersal, and pollination stability. The percentage of sufficiently pollinated florets (%SPF) decreased with the increase in daytime temperature and the duration of treatment. At a daytime temperature of 37.5 degrees C, %SPF varied widely among the cultivars and was highly correlated with the length of dehiscence formed at the basal part of the theca (r=0.930, P < 0.01, n=6) and the percentage of dehisced thecae (r=0.868, P < 0.05, n=6). The factor that better explained the variation in %SPF shifted from the length of the basal dehiscence to the percentage of dehisced thecae with increasing duration of high-temperature treatment. Thus, the process preventing pollination shifted from pollen release to anther dehiscence with the increase of exposure to a high temperature.