Variability of seed plant populations under oxidizing radiation and heat stresses in natural and laboratory conditions

Biological consequences of natural or anthropogenic impacts can often be detected by monitoring cells with chromosomal abnormalities. Here we evaluate the influence of oxidizing stress (low dose rates of ionizing radiation and heat) on pea seeds in laboratory conditions (gamma-irradiated with 7 cGy at 0.3-19.1 cGy/h, T ∼ 30°C) and on natural plantain seeds collected in a 30-km zone around a nuclear power plant (NPP) (radiation exposure ∼12 μR/h, T ∼ 40°C). These stresses decrease seed survival (S) by up to 20%, whereas the frequency of rootlet meristem cells with abnormalities (CAs) can either decrease or increase (up to twofold) depending on the seeds´ antioxidant status (AOS). The mitotic index (MI) increased up to threefold, and the correlation between CA frequency and S value decreased (|r| = 0.02). We propose that the stress induces intracellular mechanisms that regulate the number of CAs and proliferating cells. Simulations showed that an enhancing factor transmitted from cell to cell contributes significantly to variability. We conclude that cell communication and stimulation of proliferation are important and CA frequency cannot provide a sufficient description of the impact of stress.