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The effi ciency of various countermeasures (radioprotective measures) in agricultural production at the radionuclide-contaminated territories after the radiation accidents in the South Ural, at the Chernobyl NPP and NPP Fukushima I are compared. The infl uence of these accidents on the decreasing of radionuclides uptake and accumulation in plant-breading and animal-breeding products, and consequently, on internal radiation dose for the human being due to foodstuffs varies in different conditions and mainly depends on radionuclide composition of contamination, soil type and manufacturing profi le of production.

The cell divisions in pea and maize seedling root meristems were synchronized by treatment with 0.03 per cent hydroxyurea for 24 hours. At different times after block cessation (removing seedlings from hydroxyurea), i.e. according to certain phases and subphases of the mitotic cycle, the seedlings were treated with 60Co gamma-radiation at doses from 3 to 32 Gy. Evaluation of seedling radioresistance by the survival of the main root meristem on the tenth day after irradiation led to the following sequence of cell stages in order of increasing resistance. For the pea root meristem: G2, M, late G1, early S, late S, middle S and early G1. For the maize root meristem: late G2, M, G1, early S, early G2, late S and middle S.

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In radicle meristem cells of germinating seeds of the pea (Pisum sativum L) before the onset of replicative synthesis of DNA, irradiation with 2-3 krad of gamma-rays induced the incorporation of 3H-thymidine (3H-TdR). Maximum isotope incorporation was noted during the first 2 hours after irradiation. Higher doses of radiation suppressed 3H-TdR incorporation. It was not seen after gamma-irradiation of air-dried seeds, nor after fast-neutron irradiation. The replication inhibitors hydroxyurea and 5-aminouracil had no effect on the gamma-induced incorporation of 3H-TdR, Whereas caffeine and acriflavine inhibited it to some extent. It is suggested that the gamma-radiation-induced incorporation of 3H-TdR in meristem cells during the pre-replicative period may be connected with repair phenomena.