LIPID-PEROXIDATION AND ANTIOXIDANT SYSTEMS UNDER ANOXIA IN PLANTS DIFFERING IN THEIR TOLERANCE TO OXYGEN DEFICIENCY

The effects of anoxia on the activities of antioxidant systems (alpha- tocopherol and superoxide dismutase) and peroxidation of lipids (POL) were studied in roots and shoots of wheat (Triticum aestivum L.), oat (Avena sativa L.), and rice (Oryza sativa L.) seedlings. An initial PO L level was shown to be higher in wheal roots, and especially shoots, as compared to the corresponding rice organs. Anoxia enhanced POL in r oots to a greater extent than in shoots. This effect was more pronounc ed in rice seedlings tolerant to oxygen deprivation and in oat seedlin gs with a moderate tolerance than in wheat seedlings sensitive to anox ia. Similar tendencies were found in chloroplasts and mitochondria iso lated from wheat and rice seedlings. The contents of endogenous tocoph erol in wheat and rice shoots were similar and by nearly two order of magnitude higher than in roots. When alpha-tocopherol acetate was appl ied to roots, its defensive role was evident only in the cases where e ndogenous tocopherol could not effectively prevent POL activation. Oth erwise, exogenous antioxidant could exert the opposite effect, intensi fying oxidation. The system of endogenous tocopherols was shown to pla y an important role in inhibiting POL; it was evidently more active in tolerant plants. The results are discussed in relation to causes and mechanisms of higher membrane stability in plants tolerant to oxygen d eficiency.