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The article is the result of the study of the role of environmental factors of chemical nature within the framework of a model ecosystem to assess the effect of polychlorinated biphenyls on the activity level of antioxidant enzymes - superoxide dismutase, catalase and peroxidase of shepherd's purse (Capsella bursa-pastoris (L.) Medik) as a medicinal plant with a short growing season. The material of the study was sprouts, developed leaf blades, flowers and forming seeds. The activity of superoxide dismutase was determined by direct spectrophotometry, peroxidase - photoelectrocolorimetrically, catalase - permanganatometry. In response to the action of the environmental factor - polychlorinated biphenyls, it was shown that throughout the growing season there was an increase in the activity of SOD and peroxidase enzymes: for SOD at the flowering stage by 10 times with a small "jump" in activity under the primary action of PCBs (0.0005 mg / l) compared to the control. In the case of peroxidase, at the minimum concentration of PCBs in sprouts, an increase of 1.6 times was noted, however, during vegetation, a decrease of 10 times was noted, during the flowering period - 15 times. Thus, for the enzymes superoxide dismutase and catalase of shepherd's purse, the phenomenon of "paradoxical dependence "dose-effect"" was established under the influence of PCBs in a minimum concentration (0.0005 mg / l) at the MAC level. The nature of the change in peroxidase activity under the minimum (stimulating) and maximum (inhibiting) effects of PCBs in a short period of time, made it possible to assume the probable existence of a peroxidase isoform in shepherd's purse that is resistant to the action of environmental toxicants of organic nature and promotes the adaptation of the plant to changing environmental conditions with the growth of anthropogenic impact on natural ecotopes and phytocenoses.
Keywords:environmental factors, model ecosystem, phytocenoses, catalase, peroxidase, superoxide dismutase, shepherd's purse, polychlorinated biphenyls, ecotoxicants, ecotopes
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