Conditions that induce floret sterility induced by high temperature in rice

为了了解导致水稻小花不育的高温条件，在澳大利亚的Hay地区，我们在农民的稻田中进行了观察，研究了授粉、结实率和小气候之间的关系。主要结论如下：1.开花期日最高气温确实达到40 ℃以上，但极端干燥风导致的强烈蒸腾冷却使冠层温度降低.在强降温条件下，冠层迎风缘穗部温度仍达35 ℃以上，导致小花不育。在国内，我们在长江大学的大学农场进行了观察，研究了授粉、结实率和小气候之间的关系。主要结论如下：1.稻田气温不高，最高35 ℃左右.但在高湿低风条件下，穗温超过气温，有时达到38 ℃，足以诱导小花不育.杂交水稻花药基部开裂长度较小，表明杂交水稻对高温较不耐受，表明穗温是准确预测高温不育发生的重要参数。由此可见，我国水稻小花不育性的发生主要是由于高湿、低风和品种的不耐所致。

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.