Protective Effect of 24-Epibrassinolide on Barley Plants Growing Under Combined Stress of Salinity and Potassium Deficiency

Evaluation of the effects of 24-epibrassinoide (24-EBL) was done on two genotypes of barley (Hordeum vulgare L.) plants (salt tolerant-RD-2508 and salt sensitive-RD-2660) grown under combined stress of salinity and potassium deficiency. Salt-stressed (200 mM NaCl) and K-deficient plants were subjected to different concentrations of 24-EBL (1 ppm, 100 ppm, 1000 ppm) to analyse its effect on combinatorial abiotic stress. Individually both salinity stress and potassium deficit resulted in decrease of plant growth, chlorophyll content and relative water content (RWC). However, the combination of salinity stress and potassium deficient was found to be more harmful for plants. Supplementation of 24-EBL ameliorated the negative effects of combined stress and promoted the growth of stressed plants. This ameliorative effect of 24-EBL could be accounted by the improved activity of antioxidant enzymes, osmolytes such as proline and sugar that affected the oxidative stress by reducing Na+ accumulation and improved K+ concentration and K+/Na+ ratio in stressed plants. Enhancement of K+ accumulation and increase in K+/Na+ ratio through restriction of Na+ accumulation could be considered as a key feature for 24-EBL-induced tolerance along with improved RWC and chlorophyll content. 24- EBL at 100 ppm was more promising in alleviating the stress conditions. Thus, BR-induced manipulation in ion haemostasis can be a prominent trait and can be used as a criterion for developing salt stress and K-limited tolerant barely genotypes.