The spontaneous level of cytogenetic damage in three plant species (Achyrophorus maculatus (Scop.) L., Plantago lanceolata L., Plantago media L.) growing at the territory of East Ural radioactive trace was studied. The radiation resistance of plants from radioactive and control nonpolluted sites was determined. The effects of additional fractionated irradiation by different doses and the role of antioxidant systems in the formation of radioprotector effect were examined. It was shown that the level of mutation process in the plant populations growing at the radiation polluted sites is increased compared to the control populations from the pure territory. The additional acute gamma-irradiation of seeds collected from the polluted and pure territories showed the improved radiation resistance of the plants from the polluted territory. In the control population of A. maculatus in the versions with a one-hour interval between fractions, the radiation effect follows the additivity principle; in the same time, at a one-day interval between fractions, a highly significant radioprotective effect manifested most clearly in the experimental population is induced. For higher plants, the enhanced effectiveness of the functioning of antioxidant systems in plants growing at radiation polluted territories was first shown. Thus, the radioprotector mechanisms of low-dose chronic and preliminary irradiation are similar and one of these mechanisms is the activation of antioxidant systems in plants growing under conditions of chronic low-intensity irradiation for long periods of time.