Changes of SOD and CAT activities and MDA content during senescence of hybrid rice and three lines leaves

Superoxide dismutase (SOD) ,Catalase (CAT) activities and malondialdehyde (MDA) ,chloro-phyll,soluble protein contents were investigated during senescence of hybrid rice and three lines. The re-sults indicated that leaf senescence was associated with the decreases of SOD and CAT activities. A marked increase of MDA content,a product of lipid peroxidation was observed during leaf senescence. The decrease of chlorophyll and soluble protein content could be used as a criterion of senescence. CAT activity de-creased more rapidly than that of SOD during senescence of leaves. The disparity between SOD activity and CAT activity during leaf senescence might result in the formation of Oi intermediates which cause the damage of the membrane. Male sterile line senesced later than hybrid rice, restorer line, maintainer line. The relative high activities of SOD and CAT of leaves might be one of the cause of late aging of male sterile line leaves.