Abstract:  【Objective】 This paper aimed to understand the characteristics of the translocation of dry matter stored in stems and grain filling in the single segment substitution line (SSSL) and its receptor parent with different drought resistances under water-deficit irrigation during filling period. 【Method】 The SSSL W27-3-5-2-4-3-3-5-7 that carries single segment genes encoding drought resistance of Brazilian upland rice IAPAR9 and its receptor parent Huajingxian74 were used as materials and grown in split-root system. Three soil water treatments, all roots well-watered (the two halves of the trunk were irrigated well water, W/W), half-root subjected to water deficit (one half of the trunk was irrigated with well water and the other was suffered from -30kPa—-40kPa of water deficit, W/D) and all roots subjected to water deficit (two halves of the trunk were suffered from -30kPa—-40kPa of water deficit, D/D), were imposed from 7th day after anthesis to mature period. The influences of different water deficits on the yield and its components of the SSSL and its receptor parent were studied, and the changes of ABA contents in stems and grains of rice were analyzed. So the effects of deficit irrigation on the catabolism and translocation of non-structural carbohydrates (NSC) in stem and sheath and the activities of key enzymes involved the grain filling were illuminated in this paper. 【Result】 Compared with W/W treatment, the increases of ABA contents in stems and grains of D/D treatment were found obviously. The relative water content, SPAD values and photosynthetic rate of flag leaves of D/D treatment were all decreased significantly during mid-late filling period. In D/D treatment, the activities of α, β starch enzymes in stem and sheath increased obviously, while the activity of sucrose synthase decreased. However, the activities of sucrose synthase (SS), acid invertase (AINV), soluble starch synthase (SSS) and Q enzymes in grains of D/D treatment decreased remarkably during early and mid filling period. Furthermore, the contents of ABA in stems and grain of W/D treatment increased, but no significant difference between W/W and W/D was found, and the similar results were gained for the relative water content, SPAD values and photosynthetic rate of flag leaves. But the activities of SS, AINV, SSS and Q enzymes in grains of W/D treatment increased remarkably during early and mid filling period. The differences between the SSSL and its receptor parent under the deficit irrigation condition during grain filling were found obviously. The remobilized rates of NSC in stem and sheath of the SSSL were higher than those of the Huajingxian74, and the activities of enzymes, dynamic changes of matters and endogenous ABA content of SSSL involved in the metabolisms of stems and grains were responded to water deficit more sensitively than those of Huajingxian74. And so there was no clearly decrease in the yield of the SSSL under two deficit irrigation treatments. The SSSL under deficit irrigation condition showed a strong drought resistance. 【Conclusion】 The moderate soil water-deficit could favor the increase of the ABA content in all organs of rice, avail the degradation and remobilization of NSC in stems and sheath, while the production and accumulation of photoassimilates of functional leaf during filling stage were not influenced significantly by water deficit, and the yield of rice would be decreased insignificantly under moderate water-deficit condition.

Key words: rice (Oryza sativa), water deficit, yield, translocation of dry matter, grain filling