减数分裂期高温胁迫对耐热性不同水稻品种产量的影响及其生理原因

以两个耐热性不同的籼稻品种为材料，在减数分裂期进行高温(白天温度>35℃)处理，以同期自然温度(白天温度<33℃)为对照，研究减数分裂期高温对产量的影响及其生理机制。结果表明，高温处理与对照相比，显著降低了热敏感品种双桂1号的花药开裂率及花粉育性，对耐热品种黄华占影响较小；明显降低了每穗颖花数、结实率和粒重，从而使产量显著下降，其中耐热品种下降幅度小于热敏感品种；热敏感品种粒宽显著缩短，长宽比显著增大，而对耐热型品种影响不大；明显降低了水稻的根系活力和幼穗的核糖核酸(RNA)含量，显著增加了叶片丙二醛(MDA)含量和幼穗的乙烯释放速率，热敏感品种变化幅度大于耐热品种；显著增加了耐热品种叶片的抗氧化酶活性，对热敏感品种无显著影响。总之，根系活力和抗氧化保护系统能力强、RNA含量高、MDA含量低及乙烯合成少是耐热性品种在高温胁迫下保持较高产量的重要生理原因。

Effect of Heat-Stress during Meiosis on Grain Yield of Rice Cultivars Dif-fering in Heat-Tolerance and Its Physiological Mechanism

Meiosis is the most stress-sensitive period in reproduction of rice plants. However, little is known how heat-stress during meiosis affects grain yield of rice. This study investigated the development of anthers and pollens, yield components, and some physiological parameters under the heat-stress during meiosis. Two indica rice cultivars with different heat-tolerance, Shuanggui 1 (heat-sensitive) and Huanghuazhan (heat-tolerant), were pot-grown and subjected to treatments of heat-stress (the mean temperature during the day >35℃) and natural temperature (the mean temperature during the day <33℃, CK). The results showed that the heat-stress significantly reduced anther dehiscence and pollen fertility rate of Shuanggui 1, while it much less affected those of Huanghuazhan. The number of spikelets per panicle, seed-setting rate, and 1000-grain weight were significantly decreased under the heat-stress for both cultivars, leading to a significant reduction in grain yield, with a more reduction in Shuanggui 1 than in Huanghuazhan. The heat-stress treatment significantly decreased grain width of Shuanggui 1 and obviously increased ratio of length to width of grain, whereas it less affected those of Huanghuazhan. The heat-stress significantly reduced root oxidation activity and ribonucleic acid (RNA) content of young panicles, and significantly increased malondialdehyde (MDA) content of leaves and ethylene evolution rate of young panicles, and the extent of the decrease or increase was more in Shuanggui 1 than in Huanghuazhan. The heat-stress treatment significantly increased activities of peroxidase, superoxide dismutase and catalase of leaves in Huanghuazhan, while it much less affected those in Shuanggui 1. The results indicate that stronger root activity and antioxidative defense system, greater RNA content, and less ethylene synthesis and lower MDA content in rice plants during meiosis would be physiological mechanisms in maintaining a higher grain yield for a heat-tolerant cultivar under high-temperature stress.