Abstract:Plants growing on heavy metal polluted soil environment can gradually evolve into differentiated ecotypes. In a survey of plant population in Zn/Pb mining and non-mining areas in southeast China,a new Zn-hyperaccumulating ecotype of Sedum alfredii Hance was found in an old Zn/Pb mining area. The old-mining ecotype showed a thicker stem, larger leaves and greater height and biomass under both natural and controlled growth conditions, relative to the non-mining ecotype. Shoot Zn concentration in the old-mining ecotype plants which grew on old mining soils with available Zn of 105.5-325.4 mg·kg-1,ranged 4134--5000 mg·kg-1,and reached as high as 2% under control condition. Shoot Zn concentration of the old-mining ecotype plants was over 30 times higher than that of the non-mining ecotype plants growing at the same external Zn concentration in the nutrient solution culture experiment (1223.6 μmol·L-1 in nutrient solution for 12 days). The distribution of Zinc in the plant differed between the two ecotypes, being stem > leaf > roots for the old-mining ecotype and root > stem > leaf for the non-mining ecotype. Shoot/root Zn ratio exceeded 10 in the old-mining ecotype, but were always 1 for the non-mining ecotype. The results showed that the old-mining ecotype of S. alfredii Hance is a Zn-hyperaccumulating ecotype, which has evolved from long-term exposure of plants to a high Zn soil environment. The finding of this ecotype is of importance for understanding micro-evolution mechanisms of Zn tolerance and hyperaccumulation of plants ,and for providing a new material for phytoremediation of Zn contaminated soils.