Antioxidant response to cadmium in Phragmites australis plant

Phragmites ( Phragmites australis Ca. (Trin.) ex Steud) plants exposed to a high concentration of CdSO4 (50 ƒÝM) for 21 d were analysed with respect to the distribution of metal, its effects on antioxidants, the antioxidant enzymes and the redox status in leaves, roots and stolons. The highest accumulation of Cd2+ occourred in roots followed by leaves, and it was not significant in the stolons when compared with the control plants. In particular, in roots from Cd-treated plants, both the high amount of GSH and the parallel increase of glutathione-S-transferase (E.C. 2.5.1.18; GST) activity seemed to associated with an induction of the detoxification processes in response to the high cadmium concentration. Superoxide dismutase (E.C. 1.15.1.1; SOD), ascorbate peroxidase (E.C. 1.11.1.11); APX), glutathione reductase (EC 1.6.4.2; GR) and catalase (EC 1.11.1.6; CAT) activities as well as reduced and oxidised glutathione contents in samples of leaves, roots and stolons were increased in the presence of Cd2+ when compared to control plants. Despite the fact that Cd2+ has a redox characteristic not compatible with the Frenton-type- chemistry that produces active oxigen species, the antioxidant response is widespread and generic. Increased activities of antioxidant enzymes in Cd-treated plants suggest that metal tolerance in Phragmites plants might be associated to the efficiency of these mechanisms.