Effects Of Irrigation And Nitrogen Application On Active Oxygen Metabolism In Flag Leaveas And Grain Yield Of Winter Wheat

In this study,Aikang 58 was used as experimental material to investigate the effects of differentirrigations and nitrogen applications on photosynthetic indexes and antioxidant components of flag leaves in the middle and late growth stage,yield and yield components at maturity.Then,analyzing and comparing the effects of different treatments on delaying flag leaf senescence and increasing yield of winter wheat in order to find the optimal equilibrium relationship between energy consumption and crop production,and provide theoretical basis and technical support for water-saving,fertilizer-saving,high-yield and high-efficiency cultivation of winter wheat in northern Henan.The main conclusions are as follows:1.Drip irrigation and nitrogen application in the range of 0-240kg·hm^-22 could increase chlorophy ?content,net photosynthetic rate,stomatal conductance and decrease intercellular CO₂ concentration;excessive nitrogen application under drip irrigation had no significant effect on increasing transpiration rate,but this index increased with the increase of nitrogen application in the range of 0-300kg·hm^-22 under flood irrigation.2.Drip irrigation could reduce MDA production in the middle and late growth stage;under drip irrigation,increasing nitrogen application in the range of 0-240kg·hm^-22 could reduce MDA production,and beyond this range,MDA content could not be reduced or even increased significantly,while MDA content decreased significantly with the increase of nitrogen application under flood irrigation.Drip irrigation was beneficial to increase SOD,CAT,APX,GR,MDHAR activity and AsA content of flag leaves;no matter drip irrigation or flood irrigation,the activity or content of these antioxidant components could be effectively increased by applying nitrogen fertilizer in the range of 0-240kg·hm^-2,but the increase was not significant beyond this range.Drip irrigation could enhance POD activity;no matter drip irrigation or flood irrigation,300kg·hm^-22 nitrogen application could effectively enhance POD activity before the middle filling stage,but the POD activity decreased sharply at the late filling stage;although the effect of240kg·hm^-22 nitrogen application on POD activity at heading stage was not as good as 300kg·hm^-2,while it could maintain a certain intensity at critical stage of grain filling.Drip irrigation was beneficial to enhance DHAR activity at late growth stage;over all,there was no significant difference in DHAR activity between drip irrigation and flood irrigation under different nitrogen applications.In the range of 0-240kg·hm^-2nitrogen application,the GSH content under drip irrigation was higher than that under flood irrigation,while under 300kg·hm^-22 nitrogen application,the opposite is true;under drip irrigation,increasing nitrogen application in the range of 0-240kg·hm^-22 could increase GSH content,and beyond this range,GSH content could not signicantly increase or even significantly decrease,while GSH content under flood irrigation increased significantly with the increase of nitrogen application.3.The components of antioxidant system in flag leaves of wheat in the middle and late growth stage could be divided into two categories:APX,MDHAR,DHAR and AsA;SOD,POD,CAT,GR and GSH.SOD and DHAR played an important role in increasing grain yield of winter wheat and they fell into two categories,respectively.More than this,they played a key role in the antioxidant team they belonged to.4.Irrigation and nitrogen application had extremely significant effects on SOD,POD,CAT activity and AsA content in flag leaves at different growth stages;nitrogen application had extremely significant effects on APX,GR,MDHAR,DHAR activity and MDA,GSH content;the interaction between irrigation and nitrogen application had significant or extremely significant effects on GSH content.5.The metabolism of reactive oxygen species in flag leaves was closely related to photosynthetic characteristics.The chlorophy?content,net photosynthetic rate and stomatal conductance of flag leaves in the middle and late growth stage were closely related to the formation factors of yield,thus affecting the final yield;in contrast,the transpiration rate at heading and flowering stage was only related to spike number and 1000-yield weight,which affected the yield.There was a significant or extremely significant positive or negative correlation between antioxidant components in the process of scavenging reactive oxygen species.In addition,there was also a significant or extremely significant positive correlation between these antioxidant components and the final yield.6.Compared with flood irrigation,drip irrigation was beneficial to increase the final yield.The increase of grain yield under drip irrigation was mainly the result of spike number,while under flood irrigation was mainly the result of spike kernel.In the range of 0-240kg·hm^-2,yield increased with the increase of nitrogen application,and beyond this range,yield under drip irrigation decreased significantly,while flood irrigation did not change it significantly.In conclusion,the photosynthetic and antioxidant abilities of flag leaves in the middle and late growth stage were stronger and the final yield was higher under drip irrigation with 240kg·hm^-22 nitrogen application.Considering the rational allocation of water and fertilizer,drip irrigation combined with240kg·hm^-22 nitrogen application can be used as a water-saving,fertilizer-saving,high-yield and high-efficiency cultivation for winter wheat in northern Henan.