[Subcellular distribution and chemical forms of Cd and Zn in Sedum jinianum]

With water culture and by using differential centrifugation technique and sequential extraction, the subcellular distribution and chemical forms of Cd and Zn in the root, stem and leaf of Sedum jinianum were studied. In treatment 10 micromol Cd x L(-1), most of Cd in S. jinianum was in the soluble fraction of cell; while in treatment 100 miromol Cd x L(-1), the Cd in root was mainly deposited on cell wall, the Cd in stem was mainly on cell wall and in soluble fraction, and over 90% of Cd in leaf were in soluble fraction. In treatment 100 micromol Cd x L(-1), the proportion of Cd on the cell walls of root, stem and leaf increased, while that in soluble fraction decreased. In treatments 1 and 800 micromol Zn x L(-1), the Zn in root, stem and leaf mainly presented in soluble fraction; while in treatments with the Zn level between 1.0 and 800 micromol x L(-1), there were no differences in the proportions of Zn in the soluble fraction and on the cell walls of root, stem and leaf. Very low proportions of Cd and Zn were found in cell organelle. The Cd in the root, stem and leaf was predominated with NaCl- and water-extractable forms, while Zn in the plants were existed in numerous chemical forms.