Studies On The Characteristics Of Uptake And Physiological Effects Of Lead Stress On Salix Growth

The study focused on ability of uptake kinetic characteristics of lead, the effect on biomass, physiology and biochemical, soil enzymes activity under lead stress. The experimental material was Salix babylonica Linn and Salix jiangsuensis CL'J172', experimental method was hydroponic and soil culture. The main results are described as follows:1. Root length significantly decreased under lead stress. Root surface area, root volume,and average diameter of root in Salix babylonica increased under moderate lead stress, root surface area, root volume,and average diameter of root in Salix jiangsuensis CL'J172'decreased significantly exposed to lead. SOD activity, proline content and POD activity increased under moderate lead stress, but declined under extreme lead stress. Leaf soluble protein and chlorophyll content decreased under lead stress, though the trends differed for different species.2. The net concentration-dependent uptake influx of Pb in both willows were characterized by Michaelis-Menten type nonsaturating kinetic curves. The amount of lead uptake by roots of both willow species increased with lead concentration and exposed time. Root cap lead content was significantly higher than that in the mature root which suggests that the root cap was more active in the uptake of Pb.The addition of acetic and malic acids enhanced the uptake of Pb in salix roots.3. The accumulation of lead in examined salix exceeded that of contrast in a growing period. The accumulation of lead in roots increased with the increase lead concentration in the soil. At 1600mg·kg-1 Pb, roots reached maximum,being 42.63 mg·g-1. And stems and leaves reflected similar laws. The absorption of lead mainly accumulated in roots, but hardly transferred to stems and leaves. The accumulative ability of roots was larger than that of stems and leaves. The results show that biomass, root length, root surface area, root volume,and root vigor significantly decreased with the increase of Pb concentrations.4. Urease activities was depressed under lead stress. The higher the concentra-tion of Pb, the greater the effect. Phosphatase activities were depressed by Pb, though the trends differ for different Pb concentrations. Dehydrogenase activities increased with an increase of Pb concentrations.