Exposure of high temperature during anthesis in rice was expected to occur more frequently in future climates. The objectives of this study were to investigate the effects of high temperature stress on the photosynthesis and the osmoregulation substances and to reveal the mechanisms for physiological metabolism change. Two varieties of Oryza stavia L. ssp. javanica IRAT109 (thermo-tolerant) and 19 D (thermo-sensitive) were treated in phytron under high temperature of 33.5 °C. The results showed that the stomatal conductance, chlorophyll content and net photosynthesis rate decreased and the intercellular CO2 concentration increased in both of the varieties during high temperature stress. But the thermo-tolerant variety IRAT109 maintained higher level of photosynthesis than thermo-sensitive variety 19 D. For two varieties, the stomatal conductance, chlorophyll content and net photosynthesis rate in plants under high temperature for 12 d were significant different from those under natural temperature. The soluble sugar and protein contents decreased gradually and the heat stable proteins increased gradually as high temperature gone in both of the varieties during high temperature stress. The proline content increased in the beginning and decreased at the end during high temperature treatment in two varieties of rice. However, the reductions in soluble sugars and proteins in IRAT109 were smaller than those in 19 D, while the increases in heat stable protein and proline content in IRAT109 were greater than those in 19 D. The contents of soluble sugars, soluble proteins and heat stable proteins in plants under high temperature stress for 6 d, 9 d and 12 d were significant different with that under nature condition in both varieties of rice. The content of proline in plants treated for 3 d, 6d and 9d increased significantly than that under natural condition in both varieties of rice. We proposed that maintaining a higher level of photosynthesis and osmoregulation substance was the physiological basis for thermo-tolerance in Oryza stavia L. ssp. javanica.% 以耐热能力不同的两个爪哇稻Oryza stavia L. ssp. javanica品种IRAT109(耐热)和19 D(热敏感)为试验材料,对两种水稻在人工气候室进行日平均气温为33.5℃的高温处理,研究了高温胁迫对耐热能力不同的两个爪哇稻光合特性和渗透调节物质的影响,旨在揭示全球气候变暖的大背景下,耐热能力不同的爪哇稻品种对高温热害的生理代谢变化规律及响应机制.试验结果显示,高温胁迫引起爪哇稻气孔导度下降,胞间 CO2浓度升高,叶绿素含量降低,最终导致净光合速率下降,并随着胁迫时间延长而呈现逐渐下降的趋势,但耐热品种IRAT109与热敏感品种19 D相比仍能维持较高的光合作用.两种水稻中气孔导度,胞间CO2浓度,叶绿素含量,净光合速率在高温胁迫12 d后与自然温度下的植株相比差异显著.同时,高温胁迫造成两爪哇稻中可溶性糖、可溶性蛋白含量降低,且随着高温胁迫时间的延长而逐渐降低,热稳定蛋白随高温胁迫时间的延长而逐渐升高,脯氨酸含量随高温胁迫时间延长呈现先升高后降低的变化趋势.耐热品种IRAT09在高温胁迫过程中可溶性糖和可溶性蛋白的下降幅度小于热敏感品种19 D,热稳定蛋白和脯氨酸含量的上升水平高于热敏感品种19 D.高温胁迫6 d后两爪哇稻中的可溶性糖,可溶性蛋白和热稳定蛋白含量与自然温度下植株相比差异显著,在高温胁迫第3、6和9天两爪哇稻中脯氨酸含量与自然温度下的植株相比差异显著.研究结果表明,耐热爪哇稻品种在高温胁迫下维持较高的光合特性和较高的渗透调节物质含量是其耐热的生理基础.
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