Conditions that induce floret sterility induced by high temperature in rice

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The objective of this study was to understand the hot conditions that induce floret sterility in rice through the observation in hot paddy field in Australia and China.In the field of Hay in Australia, we conducted our observation in farmers' paddy fields and examined the relationship among pollination, seed set percentage and microclimate. The conclusions were as follows :1. The daily maximum temperature during flowering really reaches over 40 C, but strong transpirational cooling due to extremely dry wind decrease the canopy temperature.2. In spite of strong cooling, the panicle temperature on the windward edge of canopy was reached more than 35 C and resulted in floret sterility. But the occurrence of the sterility was negligible in management of huge farm in Hay.In China, we conducted our observation in University farm of Yangtze University and examined the relationship among pollination, seed set percentage and microclimate. The conclusions were as follows :1. The atmospheric temperature in the paddy field was not so high, around 35 C in maximum. However, when the high humidity and low wind meet, panicle temperatures exceed the air temperature and some time reach 38 C, which is enough to induce the floret sterility.2. The length of basal dehiscence of anther in hybrid rice was rather small, which indicated the hybrid rice was rather intolerant to high temperatures.These results strongly suggest that the panicle temperature is very important parameter for the precise prediction of occurrence of high temperature induced floret sterility. We concluded high humidity, low wind and intolerant cultivar induce the floret sterility in China.