Abstract:

【Objective】 The aim of the experiment is to ascertain grain filling and activities of enzymes involved in starch synthesis in rice with different drought resistant abilities under water stress. 【Method】 The experiment was carried out to study dry matter translocation of stem and sheath, grain filling and activities of enzymes involved in starch synthesis in three rice hybrids with different drought resistant abilities under both normal and drought conditions. 【Result】 The results indicated that water stress decreased dry matter weight of stem and sheath at heading and harvest stage and export amount of stems and sheath, export and transform percentage of the matter after heading, reduced grain growth potentiality, the maximum rate of grain filling and mean rate of grain filling, shortened active grain-filling period and time to reach the maximum grain-filling rate, and decreased activity of key enzymes in rice grain including soluble starch synthase (SSS), ADP glucose pyrophosphorylase (ADPGPPase) and soluble starch branch enzyme during grain filling, which was obvious less in better drought resistant cultivars than those in weaker ones. Dry matter weight of stem and sheath at heading, export amount of stems and sheath, export and transform percentage of the matter after heading were positively significant or very significant correlation with grain yield. 【Conclusion】 Under water stress, higher export and transform percentage of stem and sheath, rate of grain filling, activity of key enzymes in rice grain were the physiological basis for smaller yield reduction of better drought resistant cultivars.

Key words: rice, water stress, dry matter translocation, grain filling, enzyme activity