Cumulative Allocation Of Non-structural Carbohydrates And Photosynthetic Physiological Response To Nitrogen Fertilizer Transport In Drip Irrigated Spring Wheat

High crop yields depend on the accumulation and distribution of photosynthetic assimilates,especially the efficient functioning and redistribution of non-structural carbohydrates（NSC）to the seeds.The long-term pursuit of high fertilizer and high yield in drip irrigated wheat production in Xinjiang has resulted in high nitrogen fertilizer application and inappropriate base to chase ratios,leading to increased fertilizer waste and environmental problems that threaten the sustainable development of wheat production in Xinjiang.Therefore,to investigate the physiological mechanisms and regulatory pathways of yield and quality formation by accumulation and translocation of photosynthetic products stored in nutrient organs of drip irrigated spring wheat under different N fertilizer transport modes,and to synergistically improve wheat yield and quality,has become the key to high yield and high efficiency of wheat in Xinjiang.In this thesis,we used strong wheat Xinchun37（XC37）and medium wheat Xinchun 6（XC 6）as materials,set up different N application rates and different basal chasing ratios of N fertilizer,and used HPLC to analyze the changes of NSC and fructan metabolism of stem sheath,photosynthetic characteristics of flag leaf and seed carbon metabolism in different genotypes of wheat varieties,to clarify the N response mechanism of NSC to seed transport to improve yield,with a view to provide a better understanding of the physiological and physiological mechanisms of N fertilization in Xinjiang.The main findings are as follows.The main findings are as follows.1.Response of drip irrigated spring wheat seed yield and its composition to nitrogen.In the nitrogen reduction experiment,thousand grain weight,number of spikes,number of grains on spikes and yield showed a trend of increasing and then decreasing with decreasing nitrogen application.Compared with the CK1 treatment,the A1 treatment significantly increased 1.33%to 3.77%,2.59%to 4.84%,1.58%to 7.48%and 3.06%to 6.09%respectively;the yield of Xinchun 37 and Xinchun 6 reached The maximum value was reached under this treatment.In the N fertilizer basal chase ratio trial,the thousand grain weight,number of spikes,number of grains on spikes and yield showed a trend of increasing and then decreasing with the increase of N fertilizer basal chase ratio,with a significant increase of 5.86%～12.70%,10.93%～11.86%,9.63%～13.65%and 28.90%～34.09%under N37 treatment than N28 treatment respectively,and the correlation coefficients and direct relationship between yield and thousand grain weight,number of spikes and number of grains on spikes all showed The correlation coefficients and direct relationship between yield and number of spikes,number of spikes and number of grains were all showed as number of spikes>number of grains>weight of thousand grains.2.The effect of N fertilizer transport on photosynthetic physiology of drip irrigated spring wheat leaves.The leaf leaf area index（LAI）and the relative chlorophyll content（SPAD）of the leaves reached the highest at the germination and flowering stages,respectively,and the key photosynthetic enzyme activities of wheat flag leaves showed a gradual decrease.In the nitrogen reduction experiment,the A1 treatment(255 kg·hm^-2)resulted in higher SPAD,key photosynthetic enzyme activity,gas exchange parameters and chlorophyll fluorescence parameters,which were 6.37%-8.42%,6.21%-14.57%,4.63%-10.76%and4.17%-10.27%higher at anthesis than the CK1 treatment,respectively.In the N fertilizer basal chase ratio test,SPAD,key photosynthetic enzyme activities,gas exchange parameters and chlorophyll fluorescence parameters performed highest under N37 treatment（basal chase ratio of 3:7）,which were 7.59%to 11.77%,10.01%to 38.35%,9.21%to 16.82%and 7.53%to 22.60%higher than N28 treatment at flowering stage,respectively.Correlation and path analysis showed that increasing Fv/Fm and decreasing Ci increased yield;decreasing Ci increased spike number,spike grain number and thousand grain weight,and yield was significantly and positively correlated with photosynthetic enzyme activity,gas exchange parameters and fluorescence parameters,and XC37 showed better photosynthetic physiological characteristics.3.Response of drip irrigated spring wheat nutrient organ storage material accumulation and functioning to nitrogen.Sucrose fructosyltransferase（SST）activity and fructan content at different nodes showed a rising and then falling trend with increasing fertility,reaching a peak at lactation;fructan exohydrolase（FEH）showed a“falling-rising-falling”trend,reaching a peak at waxing.In the nitrogen reduction test,FEH enzyme activity and fructan content performed best in the remaining nodes of the A1treatment.The fructan,NSC and stem sheath dry matter translocation and contribution rates varied from16.14%to 49.38%,21.43%to 44.37%,11.14%to 33.83%and 4.60%to 35.77%,9.44%to 45.65%and4.28%to 27.44%respectively.In the nitrogen fertilizer based chase ratio trials,fructan key enzyme activity and fructan content showed the highest performance with the N37 treatment,with the remaining nodes accumulating more.The translocation and contribution of fructan,NSC and stem sheath dry matter in the stem sheath varied between 20.04%to 50.93%,23.20%to 45.27%,11.14%～38.18%and 6.89%～39.75%,9.44%～44.18%,4.28%～26.76%respectively,and XC37 fructan and NSC metabolism were more prominent.Fructans,NSC and stem sheath dry weight were all significantly positively correlated withΦ_PSⅡand highly significantly negatively correlated with F_v/Fm.4.Response of flag leaf and seed carbon metabolism to nitrogen in drip irrigated spring wheat.Flag leaf soluble sugar and sucrose contents and their key metabolic enzymes peaked at 21d post flowering,and seed sucrose and starch metabolic key enzymes peaked at 28d post flowering.In the nitrogen reduction experiment,compared with the CK1 treatment,the soluble sugar and sucrose contents and their enzyme activities of the flag leaf under the A1 treatment were significantly higher by-1.70%～6.16%,13.92%～22.33%and 13.06%～17.19%at 21d post flowering,the seed starch key enzyme was4.02%～16.80%higher at 28d post flowering,and the starch content at maturity increased by8.75%～19.39%.In the N fertilizer-based chase ratio trial,the soluble sugar and sucrose contents of flag leaves and their enzyme activities were significantly higher by 28.06%to 52.25%,17.66%to 27.17%and19.43%to 57.52%at 21 d post flowering under N37 treatment compared to N28 treatment,and the key enzyme of seed starch was higher by 15.54%to 29.16%at 28 d post flowering,and the starch content at maturity increased by 14.04%～42.80%;N46 seed sucrose key enzyme was 16.61%～34.57%higher than N28 treatment at 28d post flowering,and seed soluble sugar and sucrose contents were 23.02%～28.22%and 24.63%～35.71%higher than N28 at 7d post flowering.The higher correlation between yield and flag leaf soluble sugars,flag leaf and seed SPS enzymes,ADPG-PPase enzymes,SSS enzymes and SBE enzymes indicates that synergistic improvement in yield and quality can be ensured through appropriate nitrogen regulation.The activities of key enzymes of sucrose and starch metabolism were more sensitive to nitrogen response and more likely to accumulate more carbohydrates and starch in strong-grained wheat（XC 37）than in medium-grained wheat（XC 6）.In conclusion,the application of N at 255 kg·hm^-2or a 3:7 ratio of N fertilizer basal to chase（30%N fertilizer basal+70%N fertilizer chase）in Xinjiang wheat region can promote the accumulation and retransfer of stored photosynthetic products in nutrient organs of strong（XC37）and medium gluten（XC 6）drip irrigated spring wheat,improve the production capacity of photosynthetic material,meet the high yield requirements of Xinjiang wheat.