Modulation of salt tolerance in Echinochloa frumentacea by foliar spraying of epibrassinolide
[Objective]Soil salinization seriously affects the growth,development,and yield of the forage grass E.frumentacea.We aim to investigate the regulatory effects of epibrassinolide(EBR)on salt toler-ance of E.frumentacea and its mechanism,in order to provide a theoretical basis for its application in for-age production.[Methods]Seedlings of'Ningji 1'variety were used as materials.Based on the screening of suitable salt concentrations,control,salt(150 mmol/L NaCl),and EBR(1,10,100 μg/L),either alone or in combination,were set up.A hydroponic test was used to investigate the changes in seedling growth,stress tolerant physiology,photosynthesis,ionic homeostasis,and the expression of genes related to the signaling pathway(SOS)and antioxidant enzymes.[Results]Compared with control,seedling growth,including plant height,root length,biomass,etc.,was inhibited under salt stress.Photosynthe-sis indexes,including chlorophyll content and actual photochemical efficiency of PS Ⅱ[Y(Ⅱ)],maximum photochemical efficiency of PS Ⅱ(Fv'/Fm'),electron transport rate(ETR),photochemical quenching co-efficient(qP),etc.,as well as osmoregulatory substance(proline,soluble proteins)content and antioxi-dant enzyme(SOD,POD,CAT,and APX)activities were reduced under salt stress.Root K+,Ca2+,and Mg2+contents were decreased,while root Na+content was increased under salt stress.Leaf reactive oxygen species(superoxide anion,hydrogen peroxide)content,and cell membrane permeability(malondi-aldehyde content,relative conductivity)were increased under salt stress;gene expression was significantly down-regulated.Most of the above indexes were not significantly affected by EBR treatment alone.Spra-ying different concentrations of EBR could effectively alleviate the unfavorable changes of the above inde-xes under salt stress,and the best effect was achieved by 10 μg/L EBR.[Conclusion]Foliar spraying of EBR up-regulated the expression of SOS signaling pathway and antioxidant enzyme-related genes in the leaves of E.frumentacea seedlings under salt stress,enhanced the antioxidant and osmoregulatory abili-ties,maintained ion homeostasis in the root,protected photosynthesis and growth,and improved salt tol-erance.
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