Antioxidant status of anoxia-tolerant and -intolerant plant species under anoxia and reaeration

The redox potential of the cell, as well as the antioxidant status of the tissue, are considered to be important regulatory constituents in an adaptive response in plants. Here the involvement of active antioxidants ascorbic acid (AA), reduced glutathione (GSH) and alpha- and beta-tocopherols in reactive oxygen species scavenging, and the effect of anoxic stress on their reduction state were studied in 4 anoxia-tolerant and -intolerant plant species: Iris germanica L., Iris pseudocorus L., wheat (Triticum aestivum L. cv. Leningradka) and rice (Oryza sativa L, cv, VNIIR). The initial antioxidant content (both AA and GSH) was higher in the rhizomes of the more anoxia-tolerant Iris spp,, as compared with that of the roots of the cereals. The predominant form of ascorbate was dehydroascorbic acid (DHA) in the cereals and AA in the Iris spp, Imposition of anoxia with subsequent reoxygenation resulted in an overall depletion of the reduced forms of antioxidants, No concurrent increase in oxidised forms (DI-IA and conjugated glutathione) was observed in anoxic samples. alpha-tocopherol content in Iris spp. was in the range 1-2 mu g g(-1) fresh weight, while beta-tocophtrol content was higher in the anoxia-intolerant I. germanica (7.2 mu g g(-1) fresh weight) as compared with the tolerant I. pseudacorus (1.5 mu g g(-1) fresh weight), In I. pseudacorus, a significant decrease in alpha- and beta-tocopherol levels was observed only after long-term (45 days) anoxia. The results suggested exclusion of Ali and CSII from the redox cycling under prolonged anoxia, and a concomitant decrease in the redox state, as well as an anoxia-induced depletion of alpha- and beta-tocopherols.