Effect of Lead Stress on Growth and Physiological Properties in Torreya grandis Seedlings

Experiments were conducted on 2-year Torreya grandis seedlings treated by different concentrations of Pb namely 0(control), 700 and1400 mg/kg in 2013. 60 days later, determinations were implemented on seedling height, ground diameter, biomass, photosynthetic and physiologicalparameters such as net photosynthetic rate(Pn), stomatal conductance(Gs), etc. The result showed that 700 mg·kg-1 Pb treatment could significantlypromote growth of seedlings, with more biomass, height growth and ground diameter than that of the control, as well as Pn, Gs and transpiration rate(Tr). Ultrastructure of chloroplast had no evident difference with that of the control, but activities of superoxide dismutase (SOD), peroxidase (POD)and catalase (CAT) decreased significantly. The treatment of 1400 mg/kg of Pb inhibited the growth, with less biomass, height growth and grounddiameter than that of the control, and also Gs and (Tr). Ultrastructure of chloroplast was damaged, and superoxide anion (O2.-), H2O2 andmalondialdehyde (MDA) increased evidently, as well as SOD, POD and CAT, compared with that of the control.