Tolerance and hyperaccumulation of cadmium by a wild, unpalatable herb Coronopus didymus (L.) Sm. (Brassicaceae)

The potential of a wild, unpalatable plant Coronopus didymus was investigated for the first time in terms of its capability to tolerate and accumulate cadmium (Cd) for phytoremediation purposes. A screenhouse experiment for 6 weeks was conducted to evaluate the effect of Cd from 100 to 400mgkg^-1 on growth, biomass, photosynthetic apparatus, Cd uptake and accumulation in C. didymus plants. Application of Cd facilitates the growth of the plants whereas at higher levels a slight reduction was noticed. The concentration of Cd in roots and shoots reached a maximum of 867.2 and 864.5mgkg^-1 DW respectively, at 400mgkg^-1Cd treatment. Cd exposure increased the generation of superoxide anion (O₂^•-), H₂O₂ content, MDA level and antioxidative response (SOD, CAT and POD) in roots and shoots of C. didymus. However, a slight decline in SOD and CAT activities were noticed in roots at highest Cd treatment (400mgkg^-1). The bioconcentration (BCF) values for all the concentrations were ˃1 and the translocation factor (TF) values were ˂ 1 at lower level but reached 1 at highest Cd concentration. Thus, C. didymus satisfies the conditions required for hyperaccumulator plants and may be practically employed to alleviate Cd from contaminated soils.