Phytoextraction of cadmium and physiological changes in Solanum nigrum as a novel cadmium hyperaccumulator

It is still difficult to fully understand the physiological, biochemical, and molecular mechanisms involved in metal hyperaccumulation and how plants adjust to an adverse environment. Solanum nigrum L. is a novel Cd-hyperaccumulator, which antioxidant defense and photosynthetic CO2 fixation were investigated in this study. The results showed that the elevated heavy metal concentration, inhibiting S. nigrum growth, was accompanied by a decrease in the photosynthetic CO2 fixation. The presence of heavy metal in soil led to disturbances in the antioxidant responses, especially in superoxide dismutase, malondialdehyde, phytochelatins, and total acid-soluble thiols, which indices in S. nigrum were significantly correlated with the elevated heavy metal concentration. Whereas peroxidase activity in S. nigrum showed a slight difference and irregular change, reduced glutathione significantly decreased with increasing culturing time and elevated Cd concentration. Thus, the manipulation of antioxidant enzyme activities increases tolerance, thereby potentially increasing the uptake capacity of an organism.