Sedum alfredii Hance is a newly reported zinc （Zn） and cadmium （Cd） hyperaccumulator native to China. In this study, four populations of S. alfredii were collected from Yejiwei （YJW）, Jinchuantang （JCT） and Qiaokou （QK） lead （Pb）lZn mines located in Hunan Province as well as Quzhou （QZ） PblZn mine located in Zhejiang Province for exploring the intraspecies difference of this plant in metal accumulation. Although they grew in the PblZn spoils with relatively similar levels of Zn, Cd and Pb, remarkable differences among the four populations in tissue heavy metal concentrations were observed. The shoot Zn concentration of QZ population （11 116mglkg） was highest and nearly five times higher than that of the JCT population （1 930 mg/kg）. Furthermore, the shoot Cd concentration observed in the QZ population （1 090 mg/kg） was also highest and 144 times higher than that found in the JCT population （7.5 mg/kg）. As for Pb concentrations in the shoot of different populations, a fourfold difference between the highest and the lowest was also found. Such difference on metal accumulation was population-specific and may be significantly explained by differences in the soil properties such as pH, organic matter （OM）, and electrical conductivity （EC）. Taking biomass and metal concentration in plants into consideration, the QZ, YJW and QK populations may have high potential for Zn phytoremediation, the QZ population may have the highest potential in Cd phytoremediation, and the QK population may be the most useful in Pb phytoremediation.
[Objective]This study aimed at exploring the physiological properties of the known Cd hyperaccumulator Viola baoshanensis and the control plant Viola inconspicua to cadmium stress.[Method]After a hydroponic experiment carried in a greenhouse,plant Cd accumulations,root elongation rates,MDA contents,and antioxidant enzyme activities were determinined.[Result]Both Viola baoshanensis and Viola inconspicua showed high levels of Cd uptake growing in Cd-supplemented solution of 300 μmol/L for 12 d with Cd accumulations of 2 595 and 3 330 mg/kg in the shoots,respectively.In the cultural solution supplemented with 300 μmol/L of Cd,the root elongation rates were not affected and the MDA contents decreased significantly in Viola baoshanensis,while the root elongation rates were significantly inhibited and the MDA contents increased remarkably in Viola inconspicua,which indicated that Viola baoshanensis had the higher Cd tolerance.The superoxide dismutase（SOD）,peroxidase（POD）and catalase（CAT）activities of two Viola species were not linearly related to the middle and low Cd-supplemented concentrations（5,50 μmol/L）and had attained the tiptop in cultural solution supplemented with 100 or 300 μmol/L of Cd but declined in cultural solution supplemented with 500 μmol/L of Cd,suggesting that the contribution of antioxidative enzymes was limited to the Cd tolerance of Viola plants.The Viola inconspicua showed a strong adaptability to the middle and low concentrations of Cd.[Conclusion]Viola species could be used as potential plant resources for the phytoremediation of agriculture areas polluted with low and even middle levels of Cd.
