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 an increase in the concentration of Na₂HAsO₄.7H₂O (5 mM, 10 mM and 20 mM), a significant decrease in the seedling length, 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, CaC_l2.2H₂O and MgSO₄.7H₂O) and organic acids (pyruvate, citrate, malate, fumarate and succinate). Best results were shown by GA₃, KH₂PO₄, NaH₂PO₄ and pyruvate. An appreciable stimulation in the activity of some oxidizing enzymes, viz., catalase, catechol peroxidase and ascorbate peroxidase was noticed in seedlings growing in the presence of Na₂HAsO₄.7H₂O indicating oxidative stress. Pretreatment of mungbean seedlings with GA₃, KH₂PO₄, NaH₂PO₄.2H₂O and pyruvate helped in the reduction of oxidative stress (to some extent) and thus provided resistance to the mungbean seedlings against As-toxicity and hence has an ameliorating effect against As-induced stress.

Arsenic (As) toxicity has gained an alarming global importance now. Groundwater contamination by As has been reported from many countries with the most severe problems occurring in AsiaBangladesh, India, China and Taiwan. Among the 21 countries affected by groundwater As contamination, the largest population at risk is Bangladesh, followed by West Bengal, India. In West Bengal, concentration of As in groundwater was found to be above the maximum permissible limit (recommended value by World Health Organization (WHO) and US Environment Protection Agency (US EPA) is 0.01 mg/L) in nine districts covering an area of 38,865 sq km. This is regarded as the biggest As calamity in the world. As toxicity is a chronic problem and is currently an epidemic in West Bengal, India. Crop plants are also affected when irrigated with As contaminated groundwater resulting in reduced growth and yield.

Elevated soil As levels resulting from a long-term use of As contaminated groundwater for irrigation, inhibited the rice seed germination and seedling establishment. The percentage of seed germination was found to decrease significantly with increasing concentrations of arsenite and arsenate. Root Tolerance Index (RTI) and Relative Shoot Height (RSH) for rice seedlings decreased with increasing concentrations of arsenate (Abedin and Meharg, 2002). There is insufficient information on the response of young mungbean plants to As pollution. Therefore our objective was to study the physiological and biochemical parameters of the seedlings under As induced stress and devise ways to ameliorate it.

Environmental Sciences Journal, Arsenate Induced Oxidative Stress, Mungbean Seedlings, Arsenic Toxicity, Root Tolerance Index, Crop Plants, Groundwater Contamination, Rice Seed Germination, Biochemical Parameters, Glutathione Reductase, Phytohormones, Mungbean Plants, Colorimetric Determination, Ascorbate Peroxidase.