Effects Of Cadmium, Lead Stress On The Seed Germination And Seedling Growth In Wild Groundcover Plant Dendranthema Lavandulifolium

The systematic studies had been done with respect to the mechanisms of Cd, Pb accumulation and toxicity in Dendranthema lavandulifolium by hydroponic culture, based on the investigation of Cd, Pb on the seed germination, plant growth, physiological metabolisms in Dendranthema lavandulifolium. This study provided the theoretical background for both heavy metal toxicity mechanisms and plant resistance to heavy metal, and practical background for the phytoremediation at mining sites or contaminated soils.The main results are as follows:1. The experiments were conducted to evaluate the effects of different cadmium, lead levels on the seed germination aspects of Dendranthema lavandulifolium. The results showed that Cd had no effect on Dendranthema lavandulifolium germination rate,germination vigor,germination index when Cd concentration at 20 mg.L-1, but its vigor index and seedling length reduce with the increment of Cd concentration at 0 mg.L-1 and 100mg.L-1.Pb concentration had no effect on Dendranthema lavandulifolium germination rate,germination index,but Pb inhibitory function was enhanced in the germination vigor, vigor index and seedling length with the increment of exposure concentration. Even brown or dead seedling could be observed.2. The growth of Dendranthema lavandulifolium to the stress of Cd and Pb at different concentrations were studied by hydroponic culture. It is found that plant growth can be inhibited by Cd and Pb stress. Total root length, root surface area, root dry weight, chlorophyll contents reduce significantly with the increment of heavy metal stress, thereby Cd and Pb are more toxic to Dendranthema lavandulifolium. Cd and Pb toxicity symptoms, like slow growth, chlorisis leaves, brown roots were observed. Stronger toxicity symptoms appeare on older leaves.Taking one with another, Cd is more toxic than Pb .3. The Physiological and biochemical changes of Dendranthema lavandulifolium to the stress of Cd and Pb at different concentrations had been measured. The results show that SOD activity, MDA content,Pro content increase as Cd and Pb concentration increase. POD activity increase at 1mg.L-1 Cd , but Pb do not show significant effect on Dendranthema lavandulifolium. Both Cd(1 mg.L-1)and Pb(5 mg.L-1)stress result in the increment of soluble sugar content. It can be concluded that Dendranthema lavandulifolium is resistant to Cd and Pb stress at low concentration, while is reduce to Cd and Pb stress at high concentration.