Abstract: Radiotracer techniques were employed to characterize ⁶⁵Zn adsorption and desorption in root-cell-wall of hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) species of Sedum alfredii Hance. The results indicated that at the end of a 30 min short time radioisotope loading period, comparable amounts of ⁶⁵Zn were accumulated in the roots of the two ecotypes Sedum alfredii, whereas 2.1-fold more ⁶⁵Zn remains in NHE root after 45-min desorption. At the end of 60 min uptake period, no difference of ⁶⁵Zn accumulation was observed in undesorbed root-cell-wall of Sedum alfredii. However, 3.0-fold more ⁶⁵Zn accumulated in desorbed root-cell-wall of NHE. Zn²⁺ binding in root-cell-wall preparations of NHE was greater than that in HE under high Zn²⁺ concentration. All these results suggested that root-cell-wall of the two ecotypes Sedum alfredii had the same ability to adsorb Zn²⁺, whereas the desorption characteristics were different, and with most of ⁶⁵Zn binding on root of HE being available for loading into the xylem, as a result, more ⁶⁵Zn was translocated to the shoot.

Key words: Adsorption, Desorption, Hyperaccumulator, Sedum alfredii Hance, Zn

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