Changes in peroxidase activity. Ascorbic and dehydroascorbic acid content in Vicia Sativa grown under chronic gamma irradiation

Abstract

Plants of Vicia sativa, chronically irradiated in the gamma field at exposure rates of 5·9, 12·6, 21·2 and 42·6 r/hr were analysed periodically for modifications in peroxidase activity and in ascorbic acid (AA) and dehydroascorbic acid (DAA) content. It was found that a remarkable increase in DAA content during the first 315 hr irradiation paralleled the growth depression induced by radiation; in the same period, the AA content was not affected by radiation. If irradiation lasted longer (up to 700 hr), there occurred a sharp decrease in the AA content and a still sharper decrease in the DAA content. This last reached very low values at 600 hr. Plants recovering after 375 hr chronic exposure did not show any visible difference with respect to those left under irradiation. However, changes in AA and DAA started to appear after 11 days recovery. In the control plants, peroxidase activity showed a peak at the end of the flowering period; in the irradiated plants the maximum occurred several days earlier. The suggestion was presented that chronic irradiation induced a kind of metabolic shortening of the life cycle. The possible correlations between growth reduction, auxin content and the biochemical parameters studied are discussed with reference to the effect of radiation on plants.