Responses of hybrid poplar to cadmium stress: Photosynthetic characteristics, cadmium and proline accumulation, and antioxidant enzyme activity

The effect of two cadmium concentrations (10^-5 M and 10 ^-4 M) on growth, Cd accumulation and wlthln-plant distribution, proline (Pro) content, and the activity of superoxide dismutase (SOD), catalase (CAT), glutathione-S- transferase (GST) and glutathione peroxidase (GSH-Px) was examined in leaves and roots of poplar plants. Symptoms of Cd toxicity were evident in Cd-treated plants: stunted growth (plant height and biomass), decreased root length, and chlorosis of young leaves. Stem and leaf growth was more affected than root growth. The decreased photosynthetic activity of treated plants may have been due to lowered chlorophyll synthesis. The activity of SOD, CAT, GST and GSH-Px was altered, as was Pro accumulation. The increment of pollutant concentration in the nutrient medium was associated with higher Cd accumulation in plants. Cd in roots was -40 times higher than in leaves and stems of plants exposed to 10^-5 M Cd. Although Cd accumulation In roots was high, the potential use of this hybrid poplar for remediation of Cd-contaminated sites seems low. This is because, apart from the described growth disturbances, translocation of Cd from roots to aboveground parts is low.