Variability of Seed Plant Populations Under Oxidizing Radiation and Heat Stresses in Laboratory Experiments

The biological consequences of natural or anthropogenic impacts can often be detected by monitoring chromosomal abnormalities. Here we evaluate the influence of oxidizing stresses (low dose rates of ionizing radiation and heat) on pea seeds (a pure line of Pisum arvense) in laboratory experiments (gamma-irradiated with 7 cGy at 0.3–19.1 cGy/h, ). These stresses decreased seed survival ( ) by up to 38%, while the frequency of rootlet meristem cells with chromosome abnormalities (CAs) can decrease significantly. The mitotic index (MI) increased under radiation stress. The , MI values and CA frequencies depended on dose rates nonlinearly, and a significant correlation between the values of and CA frequency was not always observed. In our dose-rate interval, the numbers of CAs in root meristems are nonnormally distributed and display a tail, suggesting that some CAs should be described by a correlative enhancing factor. The radiation stress-induced intracellular mechanisms regulate numbers of both cells with CAs and cycled cells by both the CA correlative (communicative) factor and a stimulation to divide. Statistical simulations showed that a correlative enhancing factor (bystander effect) contributes significantly to both variability and viability. We conclude that cell communication and stimulation of proliferation are important and CA frequency alone cannot provide a sufficient description of the impact of stress.