Effects of antimony and arsenic on antioxidant enzyme activities of two steppic plant species in an old antimony mining area.

The present work was undertaken to determine strategies and antioxidant enzyme activities involved in the adaptation of two wild steppic plants (Hedysarum pallidum Desf. and Lygeum spartum L.) to the toxic environment of the abandoned antimony mining area of Djebel Hamimat (Algeria). For this purpose, soils and plants were collected in different zones coinciding with a Sb and As concentrations gradient in the soil. Antimony (Sb) and arsenic (As) were analyzed by ICP-OES in the soils and the aboveground parts and roots of the plants. Malondialdehyde (MDA) and antioxidant enzyme activities were measured by spectrometry. Results show levels of Sb and As exceptionally high in most soil and plant samples. The two species accumulate differently Sb and As in their above and belowground parts. MDA levels, in the two parts of both species, increase significantly with increasing soil Sb and As concentrations, but they are significantly higher in H. pallidum than in L. spartum. The activities of antioxidant enzymes differ significantly according to the soil metalloid concentrations, the plant species considered and the plant part. Apart from superoxide dismutase (SOD) whose activity is, overall, higher in H. pallidum than in L. spartum, the activities of all the other enzymes studied (glutathione S-transferase (GST), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX)) are generally higher in L. spartum than in H. pallidum. For both species, APX and GST are overall more active in the upper parts than in the roots, while it is the reverse for SOD and CAT. POD is more active in the upper parts than in the roots of L. spartum and the reverse applies to H. pallidum. It appears that the two studied plant species use different tolerance strategies to protect themselves against elevated As and Sb concentrations.