Abstract:

The field experiment was conducted using four rice cultivars (Nanjing 41, Wuxiangjing 14, Yangdao 6, and Shanyou 559) with the treatment of the temperature (40±0.2)℃ for five hours (10:00–15:00) at the 1st day of rice heading. The results showed that rice pollen activity decreased with the delaying flowering time under normal temperature, and significantly reduced by high temperature (P<0.05). The difference of pollen activity between under high and under normal temperatures decreased with the delaying of flowering time, with in the highest decrement in the day of treatment or the first day after treatment. Pollen germination rate on stigmas, pollen germination rate on culture medium and stainable pollen grain rate by I-KI of the four cultivars on average under high temperature were 16.00, 25.85, and 11.74 percentage points lower than those under normal temperature at that time, and 8.49, 6.63 and 6.02 percentage points lower than those under normal temperature at 4 days after treatment. The seed setting rate of four cultivars on average under high temperature were 14.04 percentage points lower than that under normal temperature at the day of treatment, and 5.95 percentage points lower than that under normal temperature at 4 days after treatment, but empty grain and unfilled grain rates of four cultivars on average under high temperature were 10.06 and 3.98 percentage points higher than those under normal temperature at the day of treatment, and 3.98 and 1.97 percentage points higher than those under normal temperature at four days after treatment, respectively. In addition, significant difference of temperature effects on pollen activity and seed setting existed among the four cultivars with the least impact in Shanyou 559. According to the regression analysis, the rates of seed setting, empty grain and unfilled grain showed a significantly linear correlation with the rates of pollen germination on stigmas and on culture medium (P< 0.05), respectively. The above results suggest that the potential heat injury of short-term high temperature to rice pollen activity and seed setting is decreased with the delaying of flowering time and that the rates of pollen germination on stigmas and an culture medium may be the suitable indicators for selective breeding of heat resistance and the prediction of heat injury probability and degree.

Key words: Rice, Heat injury, Pollen activity, Seed setting characteristics, Global warming