A study of the activity of enzymes of the antioxidant system in ontogenesis ofArabidopsis thaliana mutants tolerant to norflurazone

The activities of superoxide dismutase and guaiacol-dependent peroxidase were studied in the ontogenesis of recessive homozygous mutants ofArabidopsis thaliana Heynh.le-2 andnfz24, which are characterized by two- to threefold increases in tolerance to the herbicide norflurazone. The mutantsle-2 andnfz24 differed from the initial race Dijon in some phenotypic features, duration of ontogenetic stages, and dynamics of the superoxide dismutase and peroxidase activities in ontogenesis. A single treatment of plants with norflurazone induced an accelerated increase in the level of both enzymes in the mutants as compared to the wild type plants. Under the conditions of multiple treatment with norflurazone, the mutantsle-2 andnfz24 displayed a higher tolerance to the bleaching effect of the herbicide and were characterized by a higher level of superoxide dismutase. The data obtained suggest that the superoxide dismutase and peroxidase activities are controlled by both ontogenetic factors and stress signals. Mutations in the linesle-2 andnfz24 increase sensitivity to a stress signal or increase efficiency of an adaptive response due to long-term maintenance of a high level of the antioxidant enzymes under the conditions of stress.