[Radiation adaptive response in wheat. Phenomenology and possible mechanism]

It was demonstrated that preliminary irradiation of wheat seeds with doses of 0.10 and 0.25 Gy reduced the sensitivity to the clastogenic action of the challenge doses of gamma-irradiation at 10 and 20 Gy, but not to a doses at 50 and 100 Gy. The adaptive response (AR) was observed. It was found that the pretreatment of seeds with antioxidant (anphen and phenoxan) before the adaptive irradiation increased the AR and revealed it after the challenge dose of 50 Gy. The formed AR was observed also on the following studies of the development of plants in particular in M1 and M2. The phenomenon is genetically determined. It has been established that the frequency of aberrant cells in each variant of the experiment (exposure of seeds to a challenge dose without pretreatment; with preliminary irradiation at a conditioning dose; pretreatment with antioxidant; treatment of seeds with antioxidant followed by exposure to conditioning doses and to a challenge doses) is in inverse proportion to the observed mitotic index and that in the experiment on the whole the frequency of aberrant cells has a linear relationship to the mitotic index with a correlation coefficient near-1, the regression line passing through the point corresponding to the spontaneous mitotic index and to the spontaneous frequency of cells with aberrations. Since the obtained results can hardly be explained in terms of the repair mechanisms of adaptive response, the authors assume that they suggest the existence of a common mechanism of formation of both an adaptive response and an antimutagenic effect in plants and that this mechanism functions as a nonspecific inducible process of stimulated repopulation.