Phytoremediation of two ecotypes cadmium hyperaccumulator Bidens pilosa L. sourced from clean soils

Heavy metal concentrations accumulated by different ecotypes of the same hyperaccumulator, collected from contaminated and uncontaminated areas, were found to vary significantly. Very few studies have compared the accumulative properties of two ecotype hyperaccumulators originating from clean soils. Here we compared the Hanzhong ecotype of Bidens pilosa L. (HAE), originating from clean soil in a subtropical monsoon climate zone Hanzhong city, with the Shenyang ecotype (SHE), originating from clean soil in a temperate semi humid continental climate zone Shenyang city, and we universally observed higher Cd concentration and higher biomass in the HAE ecotype. Both HAE and SHE demonstrated similar general Cd hyperaccumulator properties in S1 soil (4.43 mg kg^-1 Cd) and S2 soil (49.79 mg kg^-1 Cd, but HAE exhibited a higher net photosynthetic rate, transpiration rate, SOD activity and greater extractable Cd concentration in its rhizospheric soil. These results might imply that some ecotypes of hyperaccumulator in different climate zone may show higher phytoextraction potential. The differences of Cd accumulation among ecotypes may be more useful for the identification of genes relevant to plant hyperaccumulation.