[Development of Scotch pine seedlings and functioning of antioxidant systems under the chronic action of lead ions]

This study has shown that the effect of Pb2+ ions (10-150 microM) on Scotch pine seedlings is manifested by a biomass decrease and a delay in development of the root system, including shortening of the main root, reduction of the lateral root formation zone, and reduction of the number of lateral roots. The ability of the root system to deposit Pb2+ ions and to perform a barrier function, preventing Pb2+ uptake into assimilating organs, has been revealed. This ability is blocked if the Pb2+ concentration in the nutrient medium exceeds 80 microM. In the case of heightened Pb2+ concentrations, the content of photosynthetic pigments in pine needles decreases, whereas that in cotyledons increases. Analysis of the proline content and the functioning of the antioxidant enzyme system (superoxide dismutase, catalase, ascorbate peroxidase, and peroxidase) shows that the presence of Pb2+ ions in a wide concentration range does not induce intensive oxidative stress in pine seedlings.