Physiological Mechanism Of Nitrogen Application Rate On Yield Formation And Nitrogen Utilization Of Winter Wheat

The growth,physiological characteristics and nitrogen uptake and utilization of wheat were closely related to wheat genotypes and nitrogen application rates.At present,there have been a lot of studies on photosynthetic physiological characteristics and molecular mechanism of leaf color mutant,but the effects of nitrogen fertilizer application on leaf color mutant wheat materials to be clarified.In this study,the Jimai5265 yellow-green leaf mutant was used as the research object,and Xinong979 and Jimai5265 were used as the control.Four nitrogen application levels(N₀:0 kg N·ha^-1,N₁:120 kg N·ha^-1,N₂:240 kg N·ha^-1,and N₃:360 kg N·ha^-1)were set in random blocks.By analyzing the regulation effects of nitrogen application rate on wheat population traits,flag leaf photosynthetic performance,nitrogen accumulation,transport and utilization,nitrogen metabolism and grain yield and quality,the response of tested wheat to nitrogen fertilizer was determined under the setting conditions of this experiment,in order to clarify the physiological mechanism of wheat material yield formation and nitrogen fertilizer utilization.It provides reference and technical support for the cultivation and management of wheat mutant materials with high light efficiency.The main results are as follows:（1）The application of nitrogen fertilizer increased flag leaf area,plant height and tiller number,and promoted dry matter accumulation（0.35%-61.13%）during the whole growth period.The plant height and tiller number of Jimai5265 yellow-green leaf mutant were lower than those of Xinong 979（3.18%-4.63%and 2.04%-15.10%）and Jimai 5265（5.65%-9.52%and 4.86%-12.85%）.（2）Application of nitrogen fertilizer increased the chlorophyll content in flag leaves of wheat（1.40%-39.95%）and photosynthetic gas parameters（net photosynthetic rate 2.58%-128.78%,transpiration rate 4.54%-121.76%,stomatal conductance 1.15%-149.81%,intercellular CO₂concentration 0.84%-46.61%）.Improved photosynthetic characteristics.The Jimai5265 yellow-green leaf mutant showed yellowish green from seedling stage to heading stage.After heading stage,the leaf color gradually deepened until normal.The relative content of chlorophyll（SPAD）in flag leaf of Jimai5265 was always lower than that of Xinong979（6.18%-16.02%）and Jimai5265（6.82%-17.53%）in early growth stage.At14 days after flowering,with the deepening of leaf color,the SPAD value was similar to that of tested wheat and compared with Xinong979 and Jimai5265,Jimai5265 yellow-green leaf mutant had better green retention effect.The photosynthetic performance of flag leaves under different nitrogen application levels was higher（net photosynthetic rate0.90%-25.51%,transpiration rate 3.10%-46.24%,stomatal conductance 6.93%-49.38%and intercellular CO₂concentration 1.00%-28.49%）.（3）Application of nitrogen fertilizer increased the amount of nitrogen uptake and translocation of nitrogen in shoot and organs at flowering and maturity stages,and promoted the distribution of nitrogen to grains.However,with the increase of nitrogen application rate,the agronomic use efficiency and partial nitrogen productivity of wheat decreased,and reached the highest values(7.07 kg·kg^-1-14.00 kg·kg^-1and 42.96 kg·kg^-1-57.35 kg·kg^-1)when the nitrogen application rate was 120 kg N·ha^-1,which signified that high nitrogen application level reduced nitrogen utilization effiency.In addition,the peak value of nitrogen utilization efficiency of Jimai5265 yellow-green leaf mutant was higher than that of Jimai5265（21.83%and 17.52%）and Xinong979（47.52%and 26.79%）.（4）Application of nitrogen fertilizer promoted the yield,panicle number,grain number per panicle and 1000-grain weight of the tested wheat,and the yield,panicle number and 1000-grain weight were positively correlated with each other.The yield,panicle number and 1000-grain weight of Jimai5265 yellow-green leaf mutant and xinong979 increased first and then decreased with the increase of nitrogen application rate,and reached the maximum value when nitrogen application rate was 240 kg N·ha^-1(yield6234.71 kg·ha^-1and 7364.37 kg·ha^-1、panicle number 475.41×10⁴·ha^-1and 540.84×10⁴·ha^-1、1000-grain weight 44.78 g and 50.92 g);Jimai5265 showed a trend of continuous increase(yield 7227.74 kg·ha^-1,panicle number 519.82×10⁴·ha^-1and 1000-grain weight 46.20 g),but the yield did not increase significantly at the nitrogen application rate of 360 kg N·ha^-1compared with 240 kg N·ha^-1.The application of nitrogen fertilizer also improved the quality of wheat,and there was a positive correlation between protein content,wet gluten content and starch content.The grain quality（protein content,wet gluten and starch content）of Jimai5265 yellow-green leaf mutant was better than that of Xinong979 and Jimai5265under different nitrogen application levels.In conclusion,although the yield of Jimai5265 yellow-green leaf mutant was lower than that of Xinong979 and Jimai5265,Jimai5265 yellow-green leaf mutant had better performance in photosynthetic gas parameters,nitrogen grain production efficiency and quality.The high nitrogen application level reduces the utilization of nitrogen fertilizer,and the growth characteristics and yield of Jimai5265 yellow-green leaf mutants,Xinong979and Jimai5265 could reach a good level at 240 kg N·ha^-1nitrogen application level.