[Cytogenetic responses of birch to stress factors].

The following range of changes in response to anthropogenic stress has been revealed in experimental birch seedlings relative to control: increased mitotic index, the range and frequency of abnormal mitoses, number of cells with persistent nucleoli, and number of cells in prophase. Cells with vacuolated cytoplasm were also observed. The mutagenic pressure on the organisms in the industrial areas of Voronezh demonstrated a trend to increase, which points to their high environmental pollution.

[Investigation of daily mitotic activity of the birch, Betula pendula Roth]. / Izuchenie sutochnoi mitoticheskoi aktivnosti u berezy povisloi.

A study was made of the daily mitotic activity in the seedling root meristem of birch trees growing in an ecologically clear area--the biological station of Voronezh State University "Venevitinovo". The peak of mitotic activity was exposed at 9 a. m. (according to winter time). The rise of mitotic index was noted at 9 and 12 p. m. due to an increase in the share of cells being in the prophase stage, and to a high number of dividing cells with persistent nucleoli. A possibility of prolongation of the mitotic cycle time is supposed to be due to cell delay in prophase stage, which may be associated with anthropogenic and nature-climatic influences on the original trees themselves and on their seed progeny. This makes it possible to consider the investigated region as only conventionally clear, because of the availability of a high recreative pressure upon the trees.

[Cytogenetic characteristics of seed progeny of trees under condition of antropogenic contamination in Voronezh town]. / Tsitogeneticheskaia kharakteristika semennogo potomstva nekotorykh vidov drevesnykh rastenii v usloviiakh antropogennogo zagriazneniia g.Voronezha.

It has been shown that in seed progeny of Quercus robur L., Pinus sylvestris L. and Betula pendula Roth. some cytogenetical characteristics vary under conditions of contamination. Such changes may be common or specific type. Thus, the frequency of pathological mitosis increases under such conditions in all the investigated species of trees. Inhibition of mitosis was found in the progeny of the pine, and variability in the number of nucleoli was detected in the pine and oak. However, in some cases the level of pathological mitosis in the oak progeny did not differ from the control, but the mitotic activity was higher due to the presence of much more cells being at the prophase stage. In the birch progeny under conditions of contamination the mitotic index increased, with a simultaneous shifts in the peaks of mitotic activity. The possibility of using these cytological characteristics for the aims of cytogenetical monitoring is considered.