Effects Of Nitrogen Application Level On Growth,Development,and Yield Under Water-Saving Condition In Winter Wheat

According to the current status that the plant growth,delopment,and yield is needed to be further investigated in winter wheat treated by water-saving condition in Hebei plain,the effects of N level on population growth traits,physiological property,and yield of winter wheat under water-saving cultivation condition?one irrigation performed at hointing stage?were studied based on a split design,in which,the wheat cultivar was acted as main plot and N application level as sub-main plot.The main results are as follows:1.The total stem numbers and leaf area index?LAI?of the two tested cultivars?i.e.,Jimai 22 and Gaoyou 2018?were both shown by a single-peak curve with the growth progression.The population biomass amounts were increased gradually with the growth development.Compared with No,N120 and N240 treatments increased the population growth traits of the two varieties.These results suggested that suitable increase of nitrogen application amount is beneficial to the population growth and development in winter wheat under water-savng cultivation condition.2.The chlorophyll contents?Chl?and photosynthetic parameters?Pn,stomatal conductance,and transpiration rate?were increased along with the increase of nitrogen supply level.In contrast,the intercellular CO₂ concentrations were decreased with the increase of nitrogen application amount.Under N0 treatment,Jimai 22displayed higher Chl and photosynthetic parameters than Gaoyou 2018,but the photosynthetic traits were similar under N240 in two cultivars.These results suggested that Gaoyou 2018 is more sensitive to N level than GY 2018.3.Compared with N0,N120 and N240 elevated the activities of cellular protective enzymes and lowered the MDA content in tested wheat cultivars.Jimai 22displayed significantly higher protective enzyme activities and lower MDA contents than Gaoyou 2018.Thus,the two tested cultivars were the best on cellular protection performance under N240 treatment.Under N0,Jimai 22 was much stronger in protecting cellular injury by low-N stress than Gaoyou 2018.4.Analysis on expression patterns of nitrate transporter?NRT?family geens and NY-Y transcription factor family genes indicated that the NRT genes TaNRT1 and TaNRT1.1 and the NF-Y family gene NFYA-B5 was up-regulated by the low nitrogen condition?N0?.This finding suggested that these differential genes are involved in plant response or adaptation to the low nitrogen stress.5.Illumina MiSeq high-throughput sequencing analysis indicated that compared with N240,totally 1835 genes were shown to be differentially expressed in leaves of Jimai 22,including that 533 were up-regulated and 1302 were down-regulated.Likewise,a total of 410 genes were found to be differentially expressed in grains,of which,223 were up-regulated and 187 were down-regulated.These differential genes were mainly involved in biological processes,cell components,and molecular functions and overrepresented by biochemical pathways of TOR signaling pathway,PI3K-Akt signaling pathway,Th1 and Th2 cell differentiation,carbon fixation in photosynthetic organisms,starch and sucrose metabolism and other pathways.These results suggested that the responses of leaves and grains to external N levels are closely associated with the modulation on transcription efficiency of a quantity of genes related to cellular structure,molecular function,and biological processes.In summary,we obtained follow conclusions:In plain areas of hebei province,the application of N240 kg·hm^-2 was easy to achieve suitable population and physiological indexes in winter wheat and the goal of high yield and high efficiency.