Effect Of Water Stress On Distribution Of Carbon Assimilation And Microstructure Of Ears In Wheat

Water is the limited factor of the growth of wheat in the north of China. Effect of drought on wheat in different growth stages was obvious,which reduced the yield of wheat seriously. In this studay, pot experiments were carried out to learn the contribution of different organs to grain weight through the treatments of defoliate, darken ear and darken stem and the microstructure of rachis in different genotype wheat under water stress. We also determinated the activity of the protective enzymes and sucrose phosphate synthase(SPS) and the photosynthesis characteristics. Main results in this study are listed as follows:1. There were significant differences among different organs in the contribution to the per ear grain weight. Compared with normal water treatment,the contribution of leaf and ear to the per ear grain weight were increased under water deficit, but decreased in the stem sheath and its reserved substance.2. Changes of SPS of flag leaf in anthesis stage were different from that in filling stage which under different water treatments. The SPS increased under the moderate water deficit,while it decreased under the severe water dificit in anthesis stage. With the level of the water stress increasing,the SPS of flag leaf decreased in the filling stage. In the heading stage , anthesis stage and in the filling stage, the Pn,Gs and Tr decreased with the level of the water stress increasing. The SPS of flag leaf in filling stage was positively correlated with the Pn.3. The number and the area of macro-vascular bundle and small-vascular bundle of rachis and the diameter of vessel and the area of phloem decreased from base to top, but the decreased rate differed with the change of the kind of vascular bundle and position of rachis. Compared with normal water treatment, the number and the area of macro-vascular bundle and small-vascular bundle of rachis and the diameter of vessel and the area of phloem decreased under moderate water deficit, while it decreased obviously under the severe water deficit. It showed that the vascular bundle system of rachis in wheat changed apparently under water deficit.4. The activities of protective enzymes of flag leaf are higher under the moderate water deficit than that of control in heading and anthesis stages while decreased under the severe water dificit; In filling stage, superoxide dismutase (SOD)activity changed apparently from different species, peroxidase (POD)activity increased under water deficit while catalase (CAT)activity changed as that in the two former stages does. Superoxide dismutase (SOD)activity in heading stage is higher than that in the other two stages, Peroxidase (POD)activity is higher than that in the other two stages, and however, catalase (CAT)activity is lower than that in the other two stages. It showed that the activities of protective enzymes changed apparently in different growth stages under water deficit.