Effects Of Different Water Treatments On Carbon And Nitrogen Metabolism,Yield And Quality Of Soybean During Filling Period

Water is an important ecological limiting factor for soybean production in Northeast China and Huang-Huai-hai region.Natural disasters such as drought and flood are often encountered in the growing season of soybean,which adversely affect the growth and development,yield and quality of soybean.Reasonable water supply is of great significance to ensure the high yield and quality of soybean.In order to deeply understand the effects of different water supply on the filling period of soybean yield and quality,and explore the physiological mechanism of soybean response to water change,three different degrees of water treatment were set with soybean varieties’ Zhonghuang 42(ZH42)’and’ Zhonghuang 76(ZH76)’of different quality types as materials: Water suitability(W0),water excess(W1)and water deficit(W2).The effects of water on grain morphogenesis,dry matter accumulation,photosynthetic physiology,osmotic regulation,carbon and nitrogen metabolism,hormone regulation,yield and quality accumulation of soybean during filling period were studied.The main conclusions were as follows:(1)Water deficit and excess water had no effect on plant height and bottom pod height.The seed length,width and weight of soybean increased with the increase of water,and the two water treatments increased the unruffed pods and the unruffed seed number,and reduced the pod number and the seed number of soybean per plant,which resulted in the decrease of yield.(2)The excess and deficiency of water at filling period reduced the SPAD value,stomatal conductance,transpiration rate,intercellular carbon dioxide concentration and net photosynthetic rate of soybean leaves,and reduced dry matter accumulation.Meanwhile,the water content and electrical conductivity of leaves were affected,and the contents of malondialdehyde,proline and soluble sugar were increased.The endogenous hormones of soybean were also involved in the response of soybean to water change.The contents of IAA decreased significantly and ABA increased significantly under the conditions of water excess and water deficit.The contents of GA and ZR varied significantly among varieties and treatments.(3)Two basic physiological processes of carbon and nitrogen metabolism of soybean were affected by water treatment at filling period.Excess and deficiency of water hinder the transfer of soluble sugars and starches from leaves to seeds.Excess water decreased the nitrogen content in the organs of the two varieties,and the activities of the key enzymes NR,GS and GOGAT in nitrogen metabolism of the two varieties slightly increased or did not change,while water deficit increased the nitrogen content in the organs and promoted the transfer of nitrogen from the vegetative organs to the grains,and decreased the activities of NR,GS and GOGAT.(4)Water treatment at filling period can change the amino acid and fatty acid components of soybean and there are differences among varieties.Water deficit could increase the protein content and decrease the fat content,while excess water could increase the fat content and decrease the protein content.The protein content per plant,fat content per plant and protein plus oil yield per plant of soybean were all the highest under suitable water condition.(5)The results of the combined analysis of the transcriptome and metabolome of the seed at the early filling period showed that,through the enrichment of the differentially expressed gene GO,there were three common differentially expressed genes in the six experimental groups after different water treatment,and these three genes may be crucial for water response.KEGG enrichment analysis of differential metabolites indicated that soybean may regulate cell growth through DNA replication and endoplasmic reticulum processing,and regulate soybean plants to adapt to different water treatments through photosynthesis,carbon metabolism,glycolysis and gluconogenesis,ABA signal regulation,etc.Osmoregulation is activated through the synthesis of secondary metabolites,the synthesis of panquinone and other terpenoids,and various metabolic pathways.In conclusion,water deficit can significantly reduce soybean quality and yield.Excessive water will not improve soybean quality,but reduce yield and waste water resources.The optimum water treatment means that the field water capacity is 70-75%,and the total amount and yield of soybean protein per plant,fat per plant and egg fat per plant are the highest,which is most conducive to realizing the synergistic improvement of soybean yield and quality.