Mechanism Of Grape Root Metabolism Under Seawater Stress

Two grape rootstocks,named Beta and 3309C,which have different salt tolerance,were used to study the effect of seawater irrigation on root growth,rhizosphere microecological environment,chlorophyll fluorescence parameters,photosynthetic capacity,and the transcriptome data to provide theoretical basis for the metabolic response of grape root under seawater stress.The results were as follows:1.The total root length,root tip number,root volume and root surface area were inhibited under seawater stress.However,the decrease in these characteristics of Beta under seawater stress was larger compared with 3309C,29.1%,23.3%,49.0%,36.3%decrease in total root length,root tip number,root volume and root surface area,respectively.2.The photosynthetic index and fluorescence parameters of grape were inhibited under sea water stress.The transpiration rate of 3309C and Beta decreased by 55.8%,71.1%,and the net photosynthetic rate under seawater stress decreased by34.1%,51.4%.The intercellular CO₂ concentrations of 3309C and Beta increased by 29.9%and 59.9%,respectively.The fluorescence parameters of 3309C and Beta decreased significantly under seawater stress.The qP,Yield and ETR of 3309C and Beta decreased by38.6%,62.9%、41.9%,62.3%、40.3%,49.2%,respectively.3.The activities of SDH,CCO,Ca²⁺-ATP enzyme,H⁺-ATP enzyme and cytochrome c/a significantly decreased under seawater stress,but hydrogen peroxide（H₂O₂）and malondialdehyde（MDA）and mitochondrial membrane permeability of grapes root under seawater stress were significantly higher.The activity of H⁺-ATPase and CCO of Beta decreased by 43.5%and 22.2%,respectively.The content of MDA and H₂O₂ of Beta were higher by 155%and 214%.4.Under seawater stress the activities of SOD,CAT,and POD,soluble sugar,starch content and root activity of grape decreased significantly.The activities of SOD and POD in the roots of 3309C and Beta were lower than those of the control by 37.8%,79.7%,33.7%and 38.9%respectively.The root activity of 3309C and Beta were lower by 29.3%and 32.6%;the number of bacteria,fungi and actinomycetes,the activities of urease and sucrase in the soil of Beta and 3309C were lower than those of the control.5.The transcriptome data of roots of two cultivars under seawater stress were compared.343up-regulated genes and 223 down-regulated genes of Beta were screened out,332 genes were up-regulated and 302 genes were down-regulated of 3309C.and among them 195 genes with significant changes in expression level in both cultivars were observed.By GO analysis and KEGG metabolic pathway analysis,the differential expressed genes were classified into 3 major GO categories and 37metabolic pathways,respectively.