| Rice is one of the most important grain crops either in China or in the world and which is susceptive to high temperature. The loss of rice production due to high temperature is about 5% of all rice production in China. It has been reported that global temperature has increased 0.74±0.18℃averagely in the past one hundred and the extreme climate events (such as extremely high temperature) may happen more frequently in the future. Thus, to understand the effect of high temperature on dry matter, yield production and leaf photosynthetic ability is important in exploring the mechanisms of heat resistance in rice.The experiment was done from May 2007 to Oct 2008. The local rice cultivar (zhongzuo 59) was used in this study, and the density was 5 plants per pot. In 2007 there are three stages (jointing and booting stage, heading and flowering stage, filling stage) and five treatments for high temperature control. Plants grown at the daily highest /night of 29/27℃, 33/27℃, 37/27℃, 41/27℃, 45/27℃. Only three temperature treatments (daily highest /night of 33/27℃, 37/27℃, 41/27℃) were taken in the jointing and booting stage. In 2008 two stages (heading and flowering stage, filling stage) and 6 treatments (32/27℃, 35/27℃, 38/27℃, 41/27℃, 35/27℃(7d), 35/27℃(9d)) were taken. Observe the impact of high temperature on the rice flag leaves, the chlorophyll, the dry matter accumulation, responses of pollen activity, pollen on stigma. And discussion the physiological basis of the response of the rice to high temperature..The results were as following:1. In this study, the leaf showed highly adaptive ability to high temperature in photosynthetic rate. As the growth period development, the photosynthetic rate increased rapidly and the recovery rate increased drastically. The results suggested that the leaf in rice may have ability to resist in high temperature stress and the changes in net photosynthetic rate may not be the reason for yield loss in rice.2. There are large differences in dry matter accumulation among treatments. The most susceptive stage the flowering stage, the next one is jointing and booting stage, and the most insensitive stage is the filling stage. Less dry matter partitioned to panicle when rice subjected to high temperature condition. On the county the dry matter partitioned to stem and sheath became more. It indicated that high temperature have the effects on the nutrition migration of rice.3. Though the yields in all stages reduced when rice subjected to high temperature stress, the heading and flowering stage showed was the most sensitive stage. And it was indicated tha pollen might be the key factor in responsible for rice yield loss. The rice yields were highly reduced under high temperature. The grain numbers at the booting, the sterile gain rate in and the 1000-grain weight in filling stage were affected the more heavily as temperature increased. The yield at heading and flowering and stages were lower than that of and booting stage, especially at filling stage, indicating that Heading and flowering stage might be the most sensitive period to high temperature stress in rice.4. By Comparing the four temperature treatments and 35℃(5), 35℃(7),35℃(9),it was showed that in the heading and flowering stage, high temperature treatments havd great influence on the rice yield than the long time treatment did, for example, rice yield havd the reduction 72.69% by 41℃treatments, while the rice yield had 31.72% reduction by the 35℃(9) treatments. When in the filling stage,long time treatments havd great influence on the rice yield than the high temperature treatments did, for example, rice yield had the 37.44% by the 35℃(9) treatments while the rice yield had 29.52% reduction by 41℃treatments.
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