Translocation and Fractions of Lead in Soil-Tobacco System

The fractions and contents of lead(Pb)in soil-plant system would influence its mobility and plant toxicity. In a pot experiment, two varieties of tobacco(Yunyan 85 and Honghuadajinyuan)were used to study the distribution of different Pb chemical fractions in soil and tobacco organs. Compared with the non-rhizospheric soil, the percentages of iron and manganese-oxides-bound Pb decreased by 3.86% to 22.33%, wheras these of carbonate-bound, organic-bound and residual Pb all increased. Applying Pb significantly decreased biomass of the two tobacco varieties, while increased Pb concentrations in tobacco organs significantly. The Pb concentrations in tobacco organs were in order of root leaf stem for Yunyan 85, and root stem leaf for Honghuadajinyuan. In control treatment, Pb mainly existed as NaCl-extractable, HAc-extractable and HCl-extractable Pb, with sum of 66.49%~72.40%, but Pb addition significantly increased concentrations of ethanol-extractable Pb, which enhanced Pb mobility. Increased HCl-extractable Pb in the stem of Honghuadajinyuan might reduce Pb transference to the leaves.