Nonlinear relationship between Sr-90 content in the Koeleria gracilis plants growing in the Semipalatinsk test site and frequency of cytogenetic alterations

To construct dose-response curves for basic biological indicators, such as mortality, fertility, ra-diation-related morbidity, genetic effects, data of experimental studies of acute radiation expo-sure carried out under controlled conditions within laboratory walls are mainly used. However, the results of experimental research cannot be applied to research of radiation effects on biological species inhabiting and growing in large territories, contaminated with the mixture of -, - and -emitting radionuclides with different penetrativeness, biological efficiency and mobility in the soil-plant system. Large scale study of impact of 90Sr in different concentrations in the Koeleria gra-cilis plants on the frequency of cytogenetic damage formation. For the study 105 experimental points on the «4A» landing in the Semipalatinsk test site were selected. The landing was earlier used for radioactive substances testing, the 90Sr concentration in plants varied between 102 and 108 Bq/kg. It was the first open-air study that allowed researchers to obtain the curve of the rela-tionship between the radioniuclide content in the plants and the frequency of cytogenetic altera-tions. The threshold for cytogenetic alterations induction in the plants below 1.58105 Bq/kg was found. At the higher 90Sr concentrations statistically significant increase (p<0.001) in the frequen-cy of cytogenetic alterations induction from <2% to 18% was observed. Among all cytogenetic disorders found in the plants double bridges and fragments occurred more frequently; it indicates that formed cytogenetic alterations were induced by radiation.