Effect Of Limited Water Supply On Some Physiological And Biochemical Mechanisms During Grain Filling Of Wheat

Shortage of water resources restricted agricultural production in arid and semiarid region. In order to mitigated contradiction between water and yields carried out limited water supply in crops. The aim is that not effect significantly yields and raises greatly water use efficiency (WUE), and integrate effectively water and yields with WUE. This research according to these problems carried out four years of pot and plot tests etc in 1999-2002, and investigated effects of yields and biomass and WUE under limited water supply during grain filling and its physiological and biochemical mechanism. Using 14C isotope trace and SDS-PAGE etc techniques research remobilization of carbon assimilate and compensative effects, and the relation of water and quality. The results as follows:1. There is slight influence of physiological characteristics of photosynthesis etc under moderate drought during grain filling of wheat, and results in some harm in crops under severe drought treatment.Pot experiment results show that the content of chlorophyll and rate of photosynthesis and transpiration and stomatal conductance and single leaf WUE in flag leaf under moderate drought stress (MS) was closed to control (CK), and declined under severe drought stress (SS), but raised in single leaf WUE. The content of soluble sugar in flags leaf under two drought treatments was higher than that of control after anthesis eight days. Between post-anthesis zero and sixteen days the content of proline of flag leaf in two drought treatment increased sharp, and then declined below control. Severe drought brings about content of soluble protein in flag leaf decased, and MS treatment approached to control.2.Moderate water deficits induced remobilization of assimilate from leaves and sheath and stems etc of fore-anthesis "temporary pool" to seeds during grain filling of wheat, reduced residual and increased rate of transportation to seeds. Severe water deficits enhanced output of 14C assimilate in ear shell and stems and accumulation in seeds. It seemed that post-anthesis water deficits improved remobilization of pre-anthesis assimilates and compensation of yields.Using 14CO2 labelled wheat in pot test on pre-anthesis seven days and measured radioactivity of organs, the results show that the output of 14C assimilate in leaves was 16.58% under MS treatment was higher than that of control and SS treatment, and rate of distribution was lowest in leaves at harvest. Severe drought enhanced large amounts oftransportation to outside in ear shell and it was two times as much as control. The output of 14C assimilates in sheath under MS and SS treatment was slight higher than that of control, and output in stems was 1.6% and 2.84% respectively, but no output in stems of control. With the drought raising the proportion of assimilate transportation to seed increased, and the input to seed under MS and SS treatment at harvest was 2.94% and 9.33% higher than that of control.3. Limited water deficits of post-anthesis in wheat raised proportion of output I4C assimilates from leaves and sheath and ear shell, increased amounts of accumulation of carbon assimilate in seeds, and so made compensative action in accumulation of dry matter of seeds.Wheat was labelled by 14C on post-anthesis fourteen days and results show that there was about 39.03%~66.92% of 14C assimilates distribution in seeds. The distribution rate of 14C assimilate in seeds under MS treatment in post-anthesis thirty-four days was 8.65% higher than that of control, and the assimilate of transportation input seeds increased 35.43% far larger than that of 20.18% of control. The distribution rate under SS treatment in seeds was obviously lower than that of control.The output of 14C assimilate in leaves under MS treatment was 17.52% and far higher than that of 8.23% of control, and in sheath it was higher than that of control. The output in leaves and sheath under SS treatment was lower than that of control. The output in stems under two water stress was slightly lower than that of control...