Cytogenetic Effects in the Populations of Dwarf Feather Grass from the Territory of Semipalatinsk Test Site

— Estimation of the cytogenetic effects in the populations of dwarf feather grass was carried out at 63 points of the site “4A” of the Semipalatinsk Test Site (Kazakhstan) that do not differ in soil characteristics and contamination with heavy metals, but contrast in the level of radioactive contamination. In the years 1953–1957, military radioactive substances were tested at the site “4A.” The dose loads on dwarf feather grass plants at this site vary in the range of 0.00036–11 Gy/growing season, and internal radiation from 90 Sr makes the main contribution to the dose absorbed by plants. It was demonstrated that the dependence of the frequency of cytogenetic effects on the dose logarithm is divided into two sections. In the range of 0.36–162 mGy, the frequency of aberrant cells does not differ statistically significantly from the control level. An increase in the dose above this limit leads to a statistically significant increase in the frequency of aberrant cells. The inflection points were also estimated for other cytogenetic parameters (120 mGy for single fragments and bridges, 141 mGy for double fragments and bridges, and 174 mGy for mitotic abnormalities). Double bridges make the main contribution to the formation of cytogenetic effects, which is additional evidence of the radiation nature of changes observed in dwarf feather grass populations.