Physiological and Biochemical Effects of γ-Irradiation on Cowpea Plants (Vigna sinensis) under Salt Stress

Soil salinity is one of the most severe factors limiting growth and physiological response in cowpea plants. In this study, the possible role of gamma-irradiation in alleviating soil salinity stress during plant growth was investigated. Increasing salinity in the soil (25, 50, 100 and 200 mM NaCl) decreased plant growth, photosynthetic pigments content, total carbohydrate content and mineral uptake compared to control, while increased total phenol content, proline, total free amino acids and lipid peroxidation. Seed irradiation with gamma rays significantly increased plant growth, photosynthetic pigments, total carbohydrate, total phenol, proline, total free amino acids and the contents of N, P, K+, Ca+2 and Mg+2 compared to non irradiated ones under salinity. On the other hand, irradiation with gamma rays decreased lipid peroxidation, Na+ and Cl- contents which may contribute in part to activate processes involved in the alleviation of the harmful effect of salt at all concentrations used (25,50 and 100 mM) except at the high concentration (200 mM). Electrophoretic studies of alpha-esterase, beta-esterase, polyphenol oxidase, peroxidase and acid phosphatase isozymes showed wide variations in their intensities among all treatments.