Comparison of physiological responses to oxidative and .heavymetal stress in seedlings of rice paddy, Oryza sativa L.

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Comparison of physiological responses to oxidative and .heavymetal stress in seedlings of rice paddy, Oryza sativa L.

Physiological responses on the bases of activities of antioxidant enzymes: peroxidase, catalase, superoxide dismutase and glutathione reductase as well as estimation of total protein, lipid peroxidation and thiols in the form of iprotein, non-protein, glutathione and phytochelatin measured in growing seedlings of paddy, Oryza sativa L. , from day 2 to 8 were compared following treatment of seeds for 5h with oxidative agents, paraquat 5 × 10-5, 10-4, 10-3 mol/L, H2O2 10-3, 5 × 10-3, 10-2 mol/L, and CdCl2 10- 5, 10- 4, 5 × 10- 3 mol/L. A significant induction of all antioxidant enzymes along with an increase in the levels of protein, lipid peroxidation and glutathione was noted in response to oxidative stress, C dCl2 induced significant peroxidase and catalase activities but not superoxide dismutase. In a marked contrast from oxidative stress, CdCl2 decreased glutathione reductase activity as well as glutathione levels but increased phytochelatin level. The different physiological responses thus underlined the crucial involvement of glutathione and phytochelatin in the oxidative and heavy metal-linduced adaptive responses respectively.