| Nitrogen is the essential nutrient element with the largest demand for plants.The application of nitrogen fertilizer has made irreplaceable contributions to the improvement of unit yield of grain crops and the guarantee of food security in China.However,excessive application of nitrogen fertilizer has led to a series of environmental problems.Improving the nitrogen efficiency of maize is one of the important ways to achieve high yield and high efficiency in agriculture,and improving the nitrogen transfer efficiency after maize anthesis is an important way to improve the nitrogen efficiency of Maize(Huang Jikun et al.,2012).Five nitrogen fertilizer gradients were used in this experiment(no nitrogen application control: CK;optimized down regulation: opt.N * 70%;optimized nitrogen application: opt.N;optimized up regulation: opt.N * 130%;farmers’ traditional fertilization: conv.n).Using two types of maize:(moderate green type: Xianyu 1266,Xianyu 335;excessive green type: Denghai 605,Zhengdan 958),the differences of maize yield,yield components,dry matter quality and nitrogen distribution under the optimal nitrogen application conditions were analyzed.At the same time,measure the nitrogen concentration of different mature types of corn at maturity,find out the differences,and explore a feasible way to improve the nitrogen transfer rate of corn.This experiment is arranged in the long-term nitrogen positioning experiment station of Quzhou Experimental Station of China Agricultural University.This experiment site is the long-term positioning experiment of wheat maize rotation established in 2007.The results showed that nitrogen application significantly increased the yield and grain nitrogen concentration of the two mature types of maize.The yield per plant of moderate green mature and excessive green mature maize was in Opt The maximum yield per plant was 140 g plant-1 and 110 g plant-1 respectively.The average grain nitrogen concentration was opt It reached the highest under N,among which the moderate green mature corn was the highest 12.7 g kg-1.The aboveground dry matter mass and nitrogen accumulation of moderate green mature maize were significantly higher than that of excessive green mature maize,which may be one of the reasons why the yield per plant of moderate green mature maize was higher than that of excessive green mature maize.In Opt Under N treatment,the yield per plant of moderate green Maturing Maize Varieties was 15%-30% higher than that of excessive green Maturing Maize Varieties.The nitrogen residue in vegetative organs of over green mature varieties was higher,among which opt In the harvest period of N treatment,the nitrogen concentrations of ear leaves and upper leaves of excessive green mature maize were higher than those of moderate green mature maize,and the nitrogen concentrations of bracts and lower stems of excessive green mature maize Zhengdan 958 were higher than those of moderate green mature maize Xianyu 335 and Xianyu 1266.Opt.The nitrogen concentrations of ear position leaves,upper leaves,bracts and lower stems of over green Mature Maize Treated with N were 47.1%,25.8%,22.9% and 30.0% higher than those of moderate green mature maize,respectively.In general,optimizing nitrogen supply can improve the yield per plant and grain nitrogen concentration of two mature maize,and ensure the yield and quality of Maize at the same time.Moderate green mature maize has less nitrogen residue in vegetative organs and is a nitrogen efficient variety.Correlation analysis of nitrogen metabolism and retransfer during silking stage,15 days after silking(15das),30 days after silking(30das),determination of spike leaf and grain,determination of glutamine synthase(GS)activity and amino acid(AA)concentration.The results show that when 15 das,CK and opt Under N and conv.n,the GS activities in Xianyu 335 grains were 9.2 umol H-1 g-1,8.6 umol H-1 g-1 and 8.6 umol H-1 g-1,respectively,which were36.4%,17.3% and 17.3% higher than that of Zhengdan 958,respectively;At 30 das,opt Under N,Xianyu 335 is 10.1 umol H-1 g-1,which is 20.0% higher than Zhengdan 958.The GS activity of Xianyu 335 was significantly higher than that of Zhengdan 958,which was a possible reason for the higher nitrogen transfer of Xianyu 335.At 30 das,AA in grain increased with the increase of nitrogen application.AA in Xianyu 335 grain was significantly higher than that in Zhengdan 958,CK and opt Under N and conv.n,Xianyu 335 was 946.65 UG g-1,1168.59 UG g-1 and 1314.47 UG g-1 respectively,which increased by 27.9%,39.5% and 23.9% compared with Zhengdan 958 respectively.It is the manifestation of higher nitrogen concentration of Xianyu 335.30 das results showed that CK and opt Under N,the Rubisco concentration of panicle leaves of Xianyu 335 was significantly lower than that of Zhengdan 958.Under CK,the Rubisco activity of Zhengdan 958 was 151 nmol min-1 g-1,and that of Xianyu 335 was only 42 nmol min-1 g-1;Opt.Under N,Rubisco of Zhengdan 958 was 560 nmol min-1 g-1,which was significantly higher than 122 nmol min-1 g-1 of Xianyu 335,which was a manifestation of higher nitrogen transfer efficiency of Xianyu 335.Measure CK and opt during 15 das and 30 das The expression of GS-1 in leaves at panicle position under N and conv.n,at 15 das,in CK and opt Under N,the expression of GS-1 in the ear position of Xianyu 335 was significantly higher than that of Zhengdan 958,and there was no significant difference between the two maize varieties under conv.n;The results of 30 das showed that the expression of GS-1 in panicle leaves of Xianyu 335 was significantly higher than that of Zhengdan 958 under three nitrogen supply levels,and the expression of GS-1 was the highest under CK treatment.This is another possible reason why Xianyu 335 has higher nitrogen transfer efficiency.At silking stage,the concentration of GS in panicle leaves of Xianyu 335 under CK was higher than that of Zhengdan 958,opt There was no significant difference between N and conv.n.15 days after flowering,under the optimized treatment,the GS concentration of spike leaf of Xianyu 335 was lower than that of Zhengdan 958.There was no significant difference in GS concentration between the two varieties under conv.N treatment,which may be the manifestation of faster senescence of leaves at ear position of Xianyu 335,and delaying maize senescence after increasing fertilizer.At 30 das,the concentration of GS in panicle leaves of Xianyu 335 was the highest under CK treatment,which was significantly higher than that of other treatments.The senescence degree of lower leaves of Maize Induced by nitrogen deficiency was different,and the senescence of lower old leaves of Xianyu 335 was more serious.The senescence of lower leaves is in response to nitrogen forms.The senescence of lower leaves of maize cultured with urea is more serious than that cultured with nitrate nitrogen.Xianyu 335 has higher nitrogen transfer efficiency than Zhengdan 958,and urea culture has higher nitrogen transfer efficiency than nitrate nitrogen culture.By sampling the three complete leaves in the lower part of the three leaf stage of hydroponic maize,then determining the transcriptome,and then performing go enrichment analysis and KEGG enrichment analysis.Under the same nitrogen application conditions,the expression differences of whole genome genes among different varieties were compared,and then the up-down genes were enriched by go enrichment analysis and KEGG enrichment analysis respectively.The results of enrichment analysis showed that under nitrate nitrogen treatment,Xianyu 335 and Zhengdan 958 were enriched by differential genes.The up-regulated genes were mainly enriched in DNA integrity,ribosome assembly,etc.,and the down-regulated genes were enriched in amino acid synthesis,carbon metabolism Carbon fixation,etc.Under urea treatment,the enrichment analysis of differential genes between Xianyu 335 and Zhengdan 958 showed that the up-regulated genes were mainly enriched in defense response and Golgi component formation,and the down-regulated genes were enriched in photosynthesis and chloroplast formation.The enrichment analysis of the same maize variety under different nitrogen forms showed that the enrichment results of Zhengdan958 urea and nitrate nitrogen showed that the results of go enrichment analysis showed that the down-regulated genes were mainly concentrated in amino acid synthesis,chloroplast components,transport system,photosynthetic carbon fixation,amino acid biosynthesis,carbon metabolism,nitrogen metabolism,etc.The results of Xianyu 335 urea and nitrate nitrogen treatment showed that the results of enrichment analysis showed that the up-regulated genes clustered in defense response and a series of catabolic processes,and the down-regulated genes clustered in photosynthesis,light response and chloroplast components. |
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