Conditions that induce floret sterility induced by high temperature in rice

本研究旨在通过对澳大利亚和中国热稻田的观察，了解诱导水稻小花不育的热条件。在澳大利亚的Hay田间，我们对农民的稻田进行了观察，考察了授粉、结实率与小气候的关系。研究结论如下：1.研究结果表明：花期日最高温度可达40℃以上，但由于极度干燥的风，强烈的蒸腾降温作用降低了冠层温度。在强降温条件下，冠层迎风缘的穗温达到35℃以上，导致小花不育。但在海伊大农场的管理中，不孕症的发生是微不足道的。在中国，我们以长江大学的大学农场为研究对象，考察了授粉、结实率与小气候的关系。研究结论如下：1.研究结果表明：稻田的大气温度不高，最高35℃左右。但在高湿低风条件下，穗部温度超过气温，有时达到38℃，足以诱导小花不育。杂交水稻花药基部开裂的长度较小，说明该杂交水稻对高温的耐受性较差。这些结果表明，穗温是准确预测高温诱导小花不育发生的重要参数。结果表明，高湿、低风和不耐型品种可诱导小花不育。

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.