Induction of Oxidative Stress and Osmolyte Accumulation In Response to Sodium Arsenate Toxicity in Mungbean Seedlings and Its Amelioration

Effect of sodium arsenate (Na2HAsO4.7H2O) on the growth and activity of few oxidizing enzymes of mungbean seedlings was investigated and it was found to have drastic effects on the growth and biochemical metabolism of germinating mungbean (Vigna radiata (L.) Wilczek cv. B-105) seedlings. With the increase in concentration of sodium arsenate (5μM, 10μM and 20μM) significant decrease in seedling length and fresh weight and dry weight of mungbean seedlings was observed. Different growth promoters were used for amelioration. Reduction in growth inhibition was achieved by pretreating the seeds with phytohormones (GA3, IAA, Kinetin), macronutrients (KH2PO4, NaH2PO4.2H2O, K2SO4, CaCl2.2H2O, MgSO4.7H2O); best results were shown by GA3, KH2PO4, NaH2PO4 and pyruvate. Under arsenate induced oxidative stress levels of proline, H2O2 and phenol content was found to be elevated. An appreciable stimulation in the activity of some antioxidant enzymes, viz., catalase, catechol peroxidase, ascorbate peroxidase, polyphenol oxidase and ascorbic acid oxidase was noticed in seedlings growing in presence of sodium arsenate indicating oxidative stress. Pretreatment of mungbean seedlings with GA3, KH2PO4, and NaH2PO4.2H2O helped in reduction of oxidative stress (to some extent) as observed by increased seedling growth and lower activities of antioxidant enzymes and lesser accumulation of osmolyte Proline. It is assumed that pretreatment with GA3, KH2PO4, and NaH2PO4.2H2O provided resistance to the mungbean seedlings against As-toxicity and hence has an ameliorating effect against As-induced stress.