24-epibrassinolide pre-treatment alleviates the salt-induced deleterious effects in medicinal pumpkin (Cucurbita pepo) by enhancement of GABA content and enzymatic antioxidants

Abstract

It is known that epibrassinolide (EBL) plays an important role in the variety of plant developmental processes and adaptation to various environmental stresses. Salt stress is one of the most important environmental problems which limit crop growth and productivity. Here, the effects of EBL pretreatment on amelioration of the adverse effects of salinity were investigated in pumpkin, especially at the establishment stage. For this purpose, uniform-sized seedlings were transplanted to plastic containers containing one-half-strength Hoagland's nutrient solution. EBL was added at 0.1 and 0.01 μM to the hydroponic medium for 5 days before stress. The plants were treated with 40 and 80 mM NaCl for inducing salinity stress. Salt stress reduced the plant growth, calcium and potassium content in leaves and roots, and these detrimental effects were alleviated when plants were pretreated with EBL. Salinity stress caused a significant increase in lipid peroxidation, sodium, and γ-amino butyric acid (GABA) content. EBL pretreatment ameliorated these effects by reducing lipid peroxidation, sodium content and increasing GABA content. The increase in activities of guaiacol peroxidase, catalase, ascorbate peroxidase, and superoxide dismutase was observed under salinity stress. Application of exogenous EBL pretreatment further increased antioxidant enzymes activities. The present work emphasizes the protective role of EBL in the regulation of antioxidant enzymes and GABA accumulation and its possible link in amelioration of stress in plants. This is the first report dealing with EBL effect on GABA content under salt stress.