We analyzed DNA damage, mitotic activity and polyploidization in Crepis capillaris callus cells during short- and long-term in vitro culture, and the influence of plant growth regulators on these processes. Changes in the concentration of growth regulators altered the stability of callus. The level of DNA damage was highly dependent on the growth regulator composition of the medium. Cytokinin at high concentrations damaged DNA in the absence of auxin. Short- and long-term callus differed in sensitivity to growth regulators. Mitotic activity changed when callus was transferred to medium with modified growth regulators. Callus cell nuclear DNA content increased with age and in response to plant growth regulators. Hormones played a role in the genetic changes in C. capillaris callus culture. We demonstrated the usefulness of C. capillaris callus culture as a model for analyzing the effect of culture conditions, including plant growth regulators, on genetic stability.

Intraspecific changes in genome size and chromosome number lead to divergence and species evolution. Heavy metals disturb the cell cycle and cause mutations. Areas contaminated by heavy metals (metalliferous sites) are places where microevolutionary processes accelerate: very often only a few generations are enough for a new genotype to arise. This study, which continues our long-term research on Viola tricolor (Violaceae), a species occurring on both metalliferous (Zn, Pb, Cd, Cu) and non-metalliferous soils in Western and Central Europe, is aimed at determining the influence of environments polluted with heavy metals on genome size and karyological variability. The genome size of V. tricolor ranged from 3.801 to 4.203 pg, but the differences between metallicolous and non-metallicolous populations were not statistically significant. Altered chromosome numbers were significantly more frequent in material from the polluted sites than from the non-polluted sites (43% versus 28%). Besides the standard chromosome number (2n = 26), aneuploid cells with lower (2n = 18-25) or higher (2n = 27, 28) chromosome numbers were found in plants from both types of site, but polyploid (2n = 42) cells were observed only in plants from the metalliferous locality. The lack of correlation between chromosome variability in root meristematic cells and genome size estimated from peduncle cells can be attributed to elimination of somatic mutations in generative meristem, producing chromosome-stable non-meristematic tissues in the peduncle.