中文摘要：

以高产杂交水稻两优培九剑叶完整叶绿体为研究对象，对其衰退进程中光能转化、抗氧化特性和超微结构变化进行了研究。剑叶净光合速率随叶片衰老而逐渐下降，叶绿素含量在衰老后期出现显著下降的趋势。叶绿体PSI和PSⅡ活性均显示先上升后降低的变化趋势，PSI活性变化相对于PSⅡ活性变化较为缓慢。Ca^2＋-ATP酶和Mg^2＋-ATP酶活性变化呈现先下降后上升最后显著下降的变化趋势。叶绿体衰老早期超氧化物歧化酶在清除活性氧对叶绿体膜系统伤害中具有重要作用，衰老后期谷胱甘肽则发挥较大作用，但抗坏血酸的作用并不明显。电镜观察显示叶绿体超微结构变化与其光合生理功能变化一致。

英文摘要：

To study the cellular biological changes of chloroplasts of flag leaves in super hybrid rice Liangyoupeijiu during senescence, the ultra-structure, photosynthetic characters and antioxidant system of chloroplasts were investigated. The results showed that the net photosynthetic rate of flag leaves was decreased gradually during senescence, the chlorophyll content in flag leaves was decreased obviously at the end of senescence, the oxygen consuming activity of PS I and the oxygen evolution activity of PS Ⅱ were both increased slightly at first and then decreased gradually. Compared with the oxygen evolution activity of PS Ⅱ, the changes in the oxygen consuming activity of PS I of chloroplasts during senescence were decreased more slowly. The activities of Ca^2＋ -ATPase and Mg^2＋ -ATPase were obviously decreased first and then increased quickly and decreased remarkably in late period of senescence. Superoxide dismutase played an important role in reducing the damage of active oxygen on the membrane system of chloroplasts in the earlier senescence of flag leaves, while glutathione played an indispensable role in late period, but the function of ascorbic acid wasn＇t obvious. The changes of photosynthetic characters were consistent with the ultra-structure changes of chloroplasts.