Single and Combined Effects of Cadmium and Lead on Seed Germination and Early Seedling Growth in Rims typhina

Cadmium (Cd) and lead (Pb) generally occur simultaneously with low concentration in soil. However, anthropogenic activities have significantly raised these non-biodegradable heavy metals and caused long-term deleterious effects on ecosystem health. To study single or combined effects of Cd and Pb on seed germination, early seedling growth and physiological response in Rhus typhina, a seed germination and sand culture experiment was established completely randomized with 0, 100, 300, and 500 mg.L-1 Pb(NO3)(2) or 0, 25, 75, 125 mg.L-1 CdCl2 individually or in combination. The present results showed seed germination and seedling growth of Rhus typhina decreased with increasing Cd and Pb, and the joint effect was more serious than single heavy metal stress. The lowest of seed germination rate (GR), germination index (GI), root length (RL) and shoot length (SL) in Rhus typhina decreased 65.85%, 73.46%, 84.33% and 61.95% compared to control in soil supplemented with combined Cd and Pb, respectively. The activity of superoxide dismutase (SOD), peroxidase (POD), malondialdehyde (MDA) and soluble protein (SP) changed significantly with increasing concentration of Cd and Pb, and MDA and POD played important roles in resisting Cd and Pb stress because of their significant correlation with seed germination and early seedling growth.