Plant Science Research, Vol. 35, 2013

Alterations in the activities of antioxidative enzymes and increase in lipid peroxidation level in germinating mungbean seeds exposed to cobalt stress

Mungbean (Vigna radiata (L.) Wilczek) seeds were subjected to germination in presence of CoCl₂.6H₂O (0.5, 1.0 and 10.0 mM) for 48 h and different physiological parameters like soluble protein content, activities of antioxidative enzymes like superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX) along with the lipid peroxidation level of the embryonic tissues were estimated in order to determined the effect of Co toxicity in germinating seeds. With increase in Co concentrations, the germination percentage decreased by 15% up to 1 mM which further reduced to 25% at 10 mM CoCl₂.6H₂O. Soluble protein content increased at 0.5 mM CoCl₂.6H₂O, but decreased further and at 10 mM concentration it was decreased by 53%. SOD activity was enhanced which indicated that there was protection against superoxide radical, but at the same time possibility of H₂O₂ accumulation as a dismutation product could not be ruled out. Since there was decrease in the activities of both catalase (CAT) and peroxidase (POX), protection against H₂O₂ was poor. Because of the alterations in the activities of these key enzymes, imposition of oxidative stress was presumed which was in fact observed in the form of increase in lipid peroxidation level in the tissues. The findings of the study indicate that Co at higher concentrations is toxic to the germinating seeds and imposition of oxidative stress might be one of the mechanisms behind such toxicity.