Abstract
Abstract— The estimation of cytogenetic effects in the crested hairgrass was conducted in 38 areas of the site “4A” of Semipalatinsk test site (Kazakhstan) that do not differ in soil characteristics and heavy metal contamination, but contrast in the level of radioactive contamination. In 1953–1957, military radioactive substances were tested at the site “4A.” Dose loads on the plants at this site vary in the range of 0.00014–15 Gy, the internal irradiation with 90Sr makes the main contribution to the dose absorbed by plants. It was demonstrated that the dose dependence splits into two sections, within which the nature of the change in the frequency of cytogenetic abnormalities with a dose is fundamentally different. In the range 0.14–250 mGy, the frequency of cytogenetic effects does not differ statistically significantly from the control level. An increase in the dose above this limit leads to linear growth in the frequency of cytogenetic abnormalities. Double bridges make a major contribution in the formation of cytogenetic effects, which is additional evidence of the radiation nature of changes observed in the populations of crested hairgrass.