Effects Of Silicon On Transformation Of Cadmium Forms In Tobacco-growing Soils And Accumulation Of Cadmium In Tobacco

Through pot experiment and soil culture experiment, this article researched the pattern of flue-cured tobacco cadmium absorption and accumulation treated by silicon, the changing pattern of cadmium forms in tobacco planting soil was researched at the same time. The results showed as follows:1. Cadmium contamination restrained tobacco growth. Finite content of silicon increased the stem length and girth, maximum leaf area and fresh weight of flue-cured tobacco. Cadmium content also related to the increasing. Silicon, to some extent, increased tobacco growth under low cadmium contamination, but restrained tobacco growth under high cadmium contamination.2. Cadmium pollution makes flue cured tobacco in chlorophyll a, chlorophyll b, carotenoid content decreased, mda content, SOD activity and soluble protein content increased, and predecessors’ studying results are basically identical.A certain concentration of silicon can alleviate cadmium pollution of flue-cured tobacco leaf chlorophyll, SOD, MDA and soluble protein of stress influence.3. In treatments of Cd0, the trend of cadmium content in tobacco is root>leaf>stem in resettling and vigorous growing stage, but performed leaf>root>stem in squaring and maturation stage. In treatments of Cd1, the trend of cadmium content in tobacco was leaf>root>stem in four stages. In treatments of Cd5, the trend of cadmium content in tobacco was leaf>root>stem in vigorous growing stage, but performed leaf>stem>root in resettling, squaring and maturation stage. Tobacco cadmium content decreased in Cd0 and Cd1 silicon adding treatments but increased in Cd5 silicon added treatments.4. The rate of cadmium accumulation was different in tobacco growth cycle, which performed vigorous growing-squaring> resettling-vigorous growing>squaring-maturation. In treatments of Cd0 and Cd1, the trend of cadmium accumulation was leaf>root>stem, but performed leaf>stem>root in treatments of Cd5.In squaring and maturation stage, basically, the trend of leaf cadmium accumulation was upper>middle>lower leaf. The total cadmium accumulation of tobacco could be decreased in silicon adding treatments.5. Basically, cadmium mobile index in soil-tobacco system is stem-leaf mobile index(MIs-l)>soil-root mobile index(MIs-r)>root-stem mobile index(MIr-s). The higher of cadmium content, the easier ofcadmium transferred to tobacco leaf. At root, the addition of silicon intercepted more cadmium in soil-tobacco system, which restrained transport and enrichment of leaf cadmium.6. In treatments of Cd0, residual cadmium content is about 90% of the total cadmium, the percentage of acid extraction and oxidizable of cadmium is low;In treatments of Cd1 and Cd5, the percentage of residual cadmium is less than Cd0, the percentage of acid extraction and oxidizable is higher than Cd0 treatments,and various forms of cadmium is acid extraction > oxidizable> residual. In Cd1 and Cd5 treatments, adding silicon can reduce acid extracting cadmium content in soil.7. In treatments of Cd1, addition of silicon decreased soil available cadmium content in soil culture experiment. Soil available cadmium content is lower as the silicon addition growing. In treatments of Cd1,soil available content decreased after increasing as the soil culture time increasing. In treatments of Cd5,the addition of silicon did not have significant effect on decreasing of soil available content. Treatments of soil available phosphorus content were Cd5>Cd1. Different silicon adding content increased cultured soil p H.