关键词: 水稻, 杂交稻, 剑叶, 衰老, 超氧物歧化酶

Abstract: The O₂^- production, scavenging capacity, photooxidation, protein content, and SOD activity were studied in leaves of Yayou 2 (indica-japonica hybrid rice) and Shanyou 63 (indica hybrid rice) at filling stage. It was shown that protein content decreased gradually with days of heading in two varieties in natural condition, and the decrease in Shanyou 63 was more than that in Yayou 2. The rate of O₂^- production and SOD activity increased from heading to 20 days after heading, then decreases but still maintained certain levels until 30 days after heading in two varieties. O₂^- production rate in Shanyou 63 was more than that of Yayou 2, but SOD activity was contrary in two varieties. In addition, the change of O₂^- and SOD under photooxidation condition was consistent with the tendency above under natural condition. It was also shown that there was negative correlation between protein degradation and O₂^- / SOD in the process of senescence in flag leaves after 20 days of heading. It is suggested that O₂^-/SOD could be used as an index of scavenging ability for O₂^- during senescence in rice.

Key words: rice, hybrid rice, flag leaf, senescence, superoxide dismutase