Regulation Mechanisms Of Nitrate Re-utilization By Ethylene In Different Nitrogen Use Efficiency Brassica Napus During Later Growth Stage

Oilseed Rape?Brassica napus L.?is one of the most important oil crops in China,which cultivated area of rape is the forefront of the world and the annual planting area is increasing.Oilseed Rape demand lots of nitrogen,but the lower nitrogen use rate directly restricts the development of rape industry.As a result,how to raise the N fertilizer efficiency has become a central issue in plant nutrition research area.Ethylene is an important endogenous hormone and signaling molecule,having multiple effects.Ethylene on the impact of nitrogen studies reported in wheat,corn and other crops more,but the research in rape is less,and its mechanism is not clear.High N efficient variety Xiangyou15?No.27?and low N efficient variety 814?No.6?as the experiment material,are taked sanding experiment.Watered 100?mol·L^-11-am-inocyclopropane-1-carboxylic acid solution?ACC?at Brassica napus at later growth stage,as ACC treatment and the control does not watered ACC solution.To investigate the regulation mechanisms of re-utilization and its relationship with nitrogen use efficiency?NUE?during the later growth stages.Simultaneously,In order to verify that the BnNRT1.5relative expression inhibited of Brassica napus,to making the transport of NO₃^-in the phloem of the leaves is reduced,higher proportion of NO₃^-accumulated in older leaves and cannot be re-utilized efficiently at the later growth stages.And Resulting in a significant reduction in NUE.Arabidopsis thaliana AtNRT1.5 mutant plants?nrt1.5?and wild type?col.0?under sanding experiment.The main results are as follows:?1?Ethylene could significantly increase the total nitrogen content in the stems of the plant during early stage pod development and harvest,and increase the total nitrogen content in grains of No.6 variety during the end of pectin development and the harvest stage.Ethylene could significantly result in lower biomass,grain yield and NUE in the harvesting stage.?2?The Soil and Plant Analyzer Development?SPAD?values of the old leaves and the new leaves were higher in the pods and flowering stage,in the old leaves.Ethylene treatment resulted in a decrease in the NO₃^-re-transport of the phloem of No.6,a significant decrease in NO₃^-content in the new leaves,and more NO₃^-leaves and cannot be reused efficiently.At the same time,ethylene significantly increased the proportion of NO₃^-in the lower leaves of the lower leaves.?3?The effect of ethylene on the activity of nitrogen-related enzymes in rape was different between different periods and different varieties.The activity of Glutamate synthetase?GS?in the old leaf was inhibited by ACC at the flowering stage,while the new leaf was inhibited in the pod of the fruit.The GS activity of the new leaf was significantly inhibited by the ACC at the fruit stage,and pods are not sensitive to ethylene.The activity of PE in the old leaves was inhibited by ACC at two periods,and the new leaves were also inhibited in the pod stage.No.27 PE activity of the old leaves or new leaves was not affected by the ACC treatment.?4?At the harvest stage,the biomass and grain yield of the mutant nrt1.5 decreased significantly,and the nitrogen efficiency based on biomass and yield was also significantly reduced.NRT1.5 gene mutations led to reduced grain and biological yield and nitrogen efficiency.?5?NRT1.5 gene increased the total nitrogen of roots,stems and old leaves at the flowering stage,increased the total nitrogen of grain and silique at harvest stage.However,due to the decrease of biomass of mutant plants,the flowering plant stem and new leaf,and the total nitrogen content of grain at harvest stage were significantly lower than wild type.The total nitrogen of the old leaf was significantly higher than that of the wild type,and the total nitrogen content of the old leaf was also higher than that of the wild type.?6?The content of NO₃^-and SPAD in the old leaves of the mutant nrt1.5 were significantly increased,and the NO₃^-content ratio_{?old leaf/new leaf?}was also significantly higher than col.0.The NO₃^-content of phloem sap was lower in nrt1.5 compared with Col.0,which suggest that mutant of nrt1.5 decrease phloem NO₃^-transport,so more NO₃^-accumulated in the old leaves,and finally lead to higher NO₃^-content ratio_{?old leaves/new leaves?}in nrt1.5,as well as the leaf SPAD value.?7?Nitrogen-related enzyme activity is one of the important factors affecting nitrogen metabolism and nitrogen efficiency.The activities of PE in nrt1.5 old leaves and new leaves were significantly lower than those in col.0,and the activity of new leaf GS in nrt1.5 was also significantly lower than that in col.0.N re-utilization efficiency was regulated by ACC significantly at the later growth stages of Brassica napus,redistribution contents of NO₃^-in phloem sap was decreased in Arabidopsis mutant?nrt1.5?or Brassica napus under ACC treatment,higher proportion of NO₃^-accumulated in older leaves and cannot be re-utilized efficiently at the later growth stages.Therefore,NRT1.5 is an effective means to improve the crop NUE by increasing N redistribution and re-utilization during the later growth stage.