A COMPARISON OF BIOCHEMICAL RESPONSES TO OXIDATIVE AND METAL STRESS IN SEEDLINGS OF BARLEY, HORDEUM-VULGARE L

Biochemical responses on the bases of activities of antioxidant enzyme s; peroxidase, catalase, superoxide dismutase and glutathione reductas e as well as estimations of total protein, lipid peroxidation and thio ls in the form of protein, non-protein, glutathione and phytochelatin measured in growing seedlings of barley, Hordeum vulgare L., from Day 2 through 8 were compared following treatment of seeds for 2 h with ox idative agents, paraquat 5 x 10(-5), 10(-4), 10(-3) M, H2O2 10(-3), 5 x 10(-3), 10(-2) M and a metal salt, CdSO4 10(-5), 10(-4), 10(-3) M. A significant induction of all antioxidant enzymes along with an increa se in the levels of protein, lipid peroxidation and glutathione was no ted in response to oxidative stress, CdSO4 induced significant peroxid ase and catalase activities but not superoxide dismutase. In a marked contrast from oxidative stress, CdSO4 decreased glutathione reductase activity as well as glutathione levels but increased phytochelatin lev el. The differential biochemical responses thus underlined the crucial involvement of glutathione and phytochelatin in the oxidative and met al-induced adaptive responses, respectively. (C) 1998 Elsevier Science Ltd. All rights reserved.