关键词: 水稻, 水分胁迫, 活性氧, 保护系统

Abstract: Abstract：【Objective】Rice is one of the main staple food crops in the world, but rice may suffer serious water stress during its growth period. Water stress during grain filling results in decreasing grain yeild, but its mechanisms of Generating and scavenging active Oxygen is unclear under continuance of the water stress. 【Method】The experiments were carried out in growth chamber to investigate the effects of water stress on superoxide free radical content(O2—), hydrogen peroxide content(H2O2)，MDA content， reduced glutathione content(GSH)，ascorbic acid content (AsA)and antioxidative enzyme activities in three hybrid rice cultivars with different drought resistant abilities under both normal and drought conditions during grain filling stage. 【Result】The results indicated that water stress aggravated the membrane lipid peroxidation in rice leaves, and it was more severe in weaker drought resistant cultivars than that in better ones. O2— and H2O2 accumulated rapidly and were more rapidly in weaker ones than that in better drought resistant cultivars. During the period of water stress, decreases of GSH content，AsA content, chlorophyll content and relative water content in better drought resistant cultivars were obvious less than those in weaker ones. Activities of superoxide dismutase(SOD), catalase(CAT) and peroxidase(POD) in leave increased obviously in 0～14d after anthesis and subsequently decreased rapidly, and those in better drought resistant cultivars were more than those in weaker ones in 0～14d after anthesis. 【Conclusion】the results showed that changes of O2— content, H2O2 content，MDA content，GSH content，AsA content and antioxidative enzyme activities correlated significantly to drought resistance of rice varieties, and better drought resistant cultivars possesses high antioxidation capacity.

Key words: Rice, Water stress, Active Oxygen, Protection System