| Wheat is one of the world's most important grain crops,and the average annual increasing value of yields,in recent years,remained at 3.78%,but the increasingly frequent droughts and other natural disasters remind us that the stability of food production should not slacken in the slightest.Irrigation and Nitrogen is an important wheat production and cultivation measures,but during the specific production practice,shortage of water resources,nitrogen pollution of the environment,low utilization rate of the both are coexistence.Most of the former researcher on the effect of the irrigation and nitrogen focused on nitrogen fertilizer use numbers,application methods,application time and the coupling of irrigation times on wheat yield,protein quality.Studies on the coupling of water and nitrogen forms on the senescence of flag leaf and starch accumulation have rarely been reported.Therefore,in order to provide more scientific cultivation of wheat high yield and good quality,the field experiment with strong gluten wheat of Zhengmai 9023 and weak-gluten wheat of Zhengmai 004 from 2008 to 2009 was conducted to study the effects of differentiIrrigation times and nitrogen forms on the changes of photosynthetic characteristics of flag leaf,flag leaf senescence,and starch accumulation characteristics.The major findings are as follows:1. The effect of different irrigation times and nitrogen forms on the diurnal variation of fluorescence and senescence-related enzymes of flag leaf after flowering, carbon metabolism of flag leaf and grains, key enzymes of starch synthesis,starch and its components content, yield and its components and so on in different cultivers of wheat were all have significant variations between different cultivars.2. There was interaction effect of water-nitrogen on the changes of original photoche-mical efficiency of flag leaf (Fv / Fm) in individual time. 3. Irrigation significantly increased the SOD activity,decreased the production rate of superoxide anion,content of proline and MDA of flag leaf after flowering at late filling stage in different gluten types of wheat.However, the effect of nitrogen forms and the water-nitrogen interactions was not the same.4. Irrigation could increase the content peak of the total soluble sugar and the sucrose of flag leaf after flowering,could increase the producing rate of the flag leafs's total soluble sugar at the middle stage of the filling in two wheat cultivers,could prolong the peak period of Zhengmai 004,could also increase the drawdown rate of the total soluble sugar and the sucrose of grains of different gluten types of wheat at early grain filling stage,could increase strong gluten cultiver's and decrease weak gluten cultiver's total soluble sugar content at the late stage of the filling,could increase the sucrose content of weak gluten cultiver .There was interaction effect of irrigation -nitrogen on the total soluble sugar in flag leaves after flowering and grains of the two gluten types of wheat.5. Increase in irrigation times could efficiently promote the activity of SS in flag leaf, activity of AGPP,SSS,GBSS in grain of the two gluten types of wheat at different times during filling stages. NH4-N(NH4HCO3) could increase the activity of SS in flag leaf,activity of AGPP,SSS,GBSS in grain of Zheng Mai 9023,but NH2-N(NH2CONH2) is better for Zhengmai 004. From the point of interaction effect of water-nitrogen, W3N3 treatment could increase all the four enzymes activity mentioned at different times during filling stages, W3N1 is better for Zhengmai 004 for whole, and W3N3 is good for increasing the activity of SSS and GBSS in grains at late grain filling stage.6. The effect of different irrigation times,nitrogen forms and the interaction on the grain starch content of Zhengmai 9023 mainly focused on early stage of filling,and the control effects of irrigation times were bigger than nitrogen forms. And for Zhengmai 004, effect of irrigation times appeared at early stage of filling, effect of nitrogen forms appeared at the early and middle stage of filling, the interaction was at the late stage,and effects of nitrogen forms were bigger than irrigation times.7. The control effects of irrigation times,nitrogen forms and its interaction on the content of amylose,amylopectin and the ratio of amlose to amylopectin were significant different between the two gluten types of wheat. The effect of irrigation and nitrogen forms on the ratio of amlose to amylopectin was bigger, and the effect of irrigation times and nitrogen forms was does not synchronize. 8. The treatment of W3N3 is optimum for the final yield and the yield components of Zhengmai 9023, and Zhengmai 004 get a better yield due to a significantly higher number of grains under the treatment of W3N1.
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