Physiological Response Of Alfalfa To Spermatine Leaching Under Saline-alkali Stress

Soil salinity and alkali stress is one of the main obstacle factors for plant growth and development.In this study,alfalfa seeds were treated with Spermidine to explore the response characteristics of Alfalfa growth,development,physiology and stress resistance to exogenous spermidine under saline-alkali stress.The enrichment patterns and differential metabolites of target functional genes related to saline-alkali stress were verified by transcriptome sequencing and metabolomic sequencing.The aim was to provide technical support for alfalfa adaptive cultivation in saline-alkali soil.Support and theoretical basis.Dongmu No.1 and Gongnong No.1 alfalfa were selected as test materials for pot cultivation.The tested soils were saline-alkali soils and laboratory incubated soils from the experimental base of Northeast Normal University in Baicheng,Jilin Province,irrigated with mixed saline-alkali solution to simulate saline-alkali soils.The experimental treatments were pure water,0.5 m M and 1 m M spermidine solution soaking for 24 hours,and pot culture for 4 months under greenhouse conditions,and pot culture for 2 months in the light incubator.The biomass,osmotic potential,soluble sugar,chlorophyll,proline,malondialdehyde,sodium,potassium and calcium ion content of alfalfa,the flow rate of sodium,potassium and calcium ion on alfalfa rhizosphere surface,the enrichment mode of differentially expressed genes in transcriptome and the enrichment mode of differentially expressed metabolites in metabolome were determined.Under saline-alkali stress,the biomass,soluble sugar,chlorophyll,proline and potassium ion contents of alfalfa seeds soaked with Spermidine increased significantly,while the content of sodium ion and malondialdehyde in leaf tissue decreased significantly.Among them,0.5 m M spermidine was the best.Transcriptome sequencing showed that spermidine immersion resulted in gene expression changes.Pathway analysis showed that these differentially expressed genes were mainly involved in protein synthesis,secondary metabolic pathways and signal transduction.Spermidine soaking can effectively promote the growth and development of Alfalfa under saline-alkali stress.Metabolite analysis showed that spermidine treatment changed the amino acid,organic acid,fatty acid and other substances in plants differently,and changed the pathway of protein synthesis,growth and metabolism of alfalfa.Spermidine soaking increased the accumulation of osmotic regulative metabolites and sodium ion efflux in alfalfa leaves,maintained the balance of osmotic potential in cells,resulting in increased salt and alkali tolerance of alfalfa.Spermidine soaking significantly changed the enrichment pattern of differentially expressed genes in alfalfa leaves,and the differentially expressed genes were up-regulated or down-regulated,and participated in the physiological metabolism of alfalfa.This study confirmed that 0.5 m M spermidine had the best effect on alleviating saline-alkali stress injury of alfalfa,indicating that exogenous spermidine could provide signal regulation for alfalfa plant growth under saline-alkali stress.