The Variety Of Cotton Root Physiology And Xylem Sap Component Under K-deficient

Abiotic stresses(drought,water,heat,salt stress,etc.)has become an important factor limiting crop production all over the world.Plant roots absorb water,mineral nutrition from soil,and synthesize metabolites like hormones,organic acids and amino acids,and proteins which are supplied to aboveground parts through the xylem vessel and regulate their growth and development.In recent decades,In recent decades,omics technology has been widely used to study the response of plants to abiotic stress.It primarily seeks to determine xylem sap composition and identify the physiological markers associated with abiotic stress hrough metabolomics,ionomics and proteomics.The experimental determinates some physiological indicators of hydroponic cultured cotton seedlings under K-deficient stress.K deficiency significantly inhibits root vitality.And,K-deficient stress led to the MDA,H2O2 and O2·-concentrations increases significantly in comparison with K-replete conditions.In conclusion,the results of the present study show that low K concentrations in the culture medium lead to the accumulation of oxidative damage in the roots of cotton seedlings and decreased root vitality and induce the responses of antioxidant enzymes(SOD,APX and GR).Determination Ca2+,Mg2+,Cu2+,Zn2+,Fe3+,K+ concentration in cotton seedling xylem SAP under K-replete and K-deficient conditions by inductively coupled plasma mass spectrometry.Compared with K-replete conditions,K-deficient stress led to Ca2+,Mg2+,Cu2+,Zn2+concentrations increases in root,cotyledon and xylem sap.These results suggest that K-deficient stress induces enhance the absorption and distribution of Ca2+,Mg2+,Cu2+,Zn2+.And these changes may be improve the ability of seedings to adapt to salt stress.Metabolomics analysis to the xylem sap of cotton seedings under K-replete and K-deficientconditions found that,K-deficient stress-induced elevated the levels of some substances.Such as,some choline substances associated with the cell membrane(Glycerophosphocholine,2-Hexenoylcholine,Caproylcholine),Several kinds of amino acids,dipeptide,alpha amino acids and aerivatives,sugar alcohol,etc.These results suggest that cell membrane may be damaged,as well as,large amounts of protein decomposition and synthesis anomaly in seedings under K-deficient stress.LC-MS/MS analysis to the xylem sap of cotton seedings and identifie 258 qualitative peptides,72 uncharaterized proteins.Among qualitative peptides,116 catered to the conditions of quantitative peptides in comparison between LK and HK.The rate of secreted proteins to the total was 90.31%,and that of classical peptide was 56.98%.For the qualitative peptides in comparison,the rate was 93.97%,and that of classical peptides was 68.97%.Glycosyltransferases(GTs),glycoside hydrolases(GHs)and expansin-like proteins were down-regulated by potassium deficiency or non-detectable under potassium deficiency,suggesting cell wall metabolism was obviously inhibited by potassium deficiency.The significantly decreased or lacking FLAs or AGPs and peroxidases suggested potassium deficiency lowered pre-formed mechanical and biochemical resistance of the cotton root cell wall to pathogens attack.PR-proteins were significantly down-regulated or lacked under LK,especially for class III peroxidases,indicating the weak passive defense.In this respect,improving potassium management also can enhance plant resistance to environment by positively affecting many gene expressions,which may work in a more wide scope,compared with biotechnological methods.