Metal tolerance and phytoremoval ability in Amaranthus paniculatus L. grown in nickel-spiked nutrient solution

To evaluate a possible utilization in the phytoremediation of metal contaminated substrates, Amaranthus paniculatus L. plants were grown for one week in Ni-spiked growth solutions at 0, 25, 50, 100, 150 ?M NiCl2 in hydroponics under controlled climate conditions. Results showed a high tolerance to Ni in plants exposed to low Ni concentrations. Tolerance decreased as Ni concentration in the growth solutions enhanced. Ni concentrations in plant organs (root, stem and leaves) revealed a trend to increase in parallel with the enhancement of Ni content in the growth solution. The ability to accumulate Ni in plants was also evaluated by calculating the bioconcentration factor (BCF). An inverse relation between BCF and Ni concentrations in the growth solution was evidenced. Ni phytoremoval ability of A. paniculatus plants was particularly appreciable at 25 ?M NiCl2, where more than 65% of the initial Ni amount was taken up by plants in one week of treatment. The capability of plants to translocate Ni from roots to shoots (stem+leaves) was evaluated by the translocation factor (Tf). Results revealed a low Tf in plants exposed to low Ni concentration, suggesting a tolerance mechanism to protect physiological processes occurring in leaves. Overall, A. paniculatus plants showed a valuable capability to phytodecontaminate Ni-polluted waters, particularly at low Ni concentrations.