Abstract: Draught and irrigation regime

have been attracted more and more attention because of limited water resources in China.Rice is one of the main stable food crops in the world, and may suffer serious water stress during its growth period. Grain yield under different irrigation regimes during grain filling, and its physiological mechanism are unclear. So the experiments were carried out using three hybrid rice of Gangyou 527, D you 363, and Shanyou 63 in potted and farmland experiments to investigate the effects of four irrigation regimes [dry cultivation (DC), damp irrigation (DI), the treatment C that controlled damp irrigation before booting stage, shallow irrigation at booting stage, wetting-drying alternation irrigation from heading stage to mature stage, and submerged irrigation (SI)] on photosynthetic rate, osmotic regulators, antioxidant enzyme activities, and grain yield. The results indicated that the treatment C and DI had high chlorophyll content in flag leaf, with slow senescence of flag leaf and high photosynthetic rate (P_n) of flag leaf. Both the treatment C and DI promoted the accumulation of soluble sugar content, amino acids content, and proline content, etc., and enhanced the catalase (CAT) and peroxidase (POD) activities, which maintains the natural metabolism of cells. However, compared with submerged irrigation, changes of these substances were sensitive to water stress of DC. It was showed that grain yield of the treatment C was the highest. Grain yield and its components were significantly higher under DI than under SI, but the potential of enhancing grain yield was slightly weaker under DI than under the treatment C. Decreases of grain yield and its components were obviously less than those of the treatment C. These results suggested that photosynthetic rate, osmotic regulators content antioxidant enzyme activities, and grain yield are correlated significantly to drought resistance of rice cultivars.

Key words: Paddy rice, Irrigation regime, Grain filling stage, Physiology characteristic