Phytoremediation potential of Pterocypsela laciniata as a cadmium hyperaccumulator.

To identify new cadmium (Cd) hyperaccumulators, the artificially high soil Cd concentration method was used to screen six common farmland weeds. Among them, only Pterocypsela laciniata (Houtt.) C. Shih showed characteristics of a Cd hyperaccumulator and was selected for further studies. In pot experiments, soil Cd concentrations of 5, 10, and 25 mg kg-1 increased the biomass and photosynthetic pigment concentrations in P. laciniata when compared with the control, whereas 75 and 100 mg kg-1 decreased them (the maxima were at 10 mg kg-1 soil Cd). The antioxidant enzyme activities and the soluble protein concentrations of P. laciniata showed similar trends as biomass. The Cd concentrations in roots and shoots of P. laciniata increased as soil Cd concentration increased. When the soil Cd concentration was 50 mg kg-1, the Cd concentration in the shoots of P. laciniata was 116 mg kg-1 (the critical value for Cd hyperaccumulators is 100 mg kg-1). Both the root and shoot bioconcentration factors of P. laciniata were larger than 1.0, and the translocation factor exceeded 1.0 in almost all treatments. The Cd extractions by the shoots and whole plants of P. laciniata reached maxima at 208 and 375 μg plant-1, respectively. The Cd extractions by P. laciniata were different between two ecotypes. Therefore, P. laciniata is a Cd hyperaccumulator that could remediate Cd-contaminated soils, but the ecotypes should be considered when using P. laciniata for phytoremediation.