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水稻灌浆期耐热性的研究具有十分重要的理论与实践价值。研究结果表明,不同品种的耐热性存在极显著的遗传差异,以垩白米率、垩白大小、垩白度、秕粒率、受精粒重、饱粒重、籽粒充实度、饱粒密度等8项性状的耐热指数为指标,应用主成分分析法将其综合成3个彼此不相关的综合指标,再运用隶属函数值法求出每一品种耐热性的综合评价值,可较为全面、准确地对各品种的耐热性进行综合评价。耐热性强的品种高温胁迫后,剑叶的光合速率下降幅度明显较小,胁迫解除后恢复的程度也更高,叶绿素含量、RuBPc活性及内源多胺含量的变化趋势与光合速率相一致,是水稻耐高温逼熟的重要生理特征。高温胁迫导致水稻叶片叶绿素含量降低,表现出明显的降解作用,存在一个活性氧的伤害机理。50℃热致死时间所表示的细胞膜热稳定性可作为今后水稻灌浆期耐热性育种中适合单株选择鉴定的简便、准确的生理指标。采用生理育种途径,已育成了3个耐高温逼熟的优质、高产早籼稻新品种。
Research on the heat tolerance of rice during grain filling has very important theoretical and practical value. The results showed that there were extremely significant genetic differences in the heat tolerance of different cultivars. The chalkiness rate, chalky grain size, chalky grain size, grain size, grain weight, grain weight, grain filling degree and grain filling density 8 characters of the heat resistance index as an indicator, using principal component analysis to synthesize into three comprehensive indicators unrelated to each other, and then use the membership function value obtained for each variety of heat-resistant comprehensive evaluation value can be more comprehensive , Accurately evaluate the heat resistance of all varieties. After heat stress, the photosynthetic rate of flag leaves decreased significantly, and the degree of recovery after stress relieving was also higher. The trend of chlorophyll content, RuBPc activity and endogenous polyamine content was consistent with photosynthetic rate , Is an important physiological characteristics of high-temperature ripening of rice. Under high temperature stress, the content of chlorophyll in rice leaves decreased, showing obvious degradation effect, and there was an injury mechanism of reactive oxygen species. The thermal stability of the cell membrane expressed by the lethal time at 50 ℃ can be used as a simple and accurate physiological index for selecting and identifying the suitable plants in the heat-resistant breeding during rice grain filling stage in the future. Physiological breeding methods have been adopted, and three high-yielding and high-yielding early indica rice varieties have been bred.