Effects of heavy metals on antioxidant activities of Atriplex hortensis and Atriplex rosea.

In the present study, the effects of heavy metals generating antioxidative defense systems such as superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11) glutathione reductase (GR, EC 1.6.4.2) and catalase (CAT, EC 1.11.1.6) were studied in the leaves of Atriplex plants grown in polluted soil with different heavy metals (Cu, Ni, Pb and Zn). The results showed that the exposure of plants to different levels of metals reduced the dry matter production and height of shoots. The decrease in root growth caused by the toxicity of metals was severe than the decrease in shoot growth. Atriplex showed gradual decrease in height following metal treatments, a four week exposure of A. hortensis var. rubra L. (red) to 25%,50%,75% and 100% contaminated soil gave a respective mean values of 21.4, 12.2, 9.3 and 6.5 cm which were lower in comparison to the plants of the control group. Of the antioxidant enzymes, the results showed that SOD and APX, were diminished by metal toxicity. However, the activity of CAT and GR were increased by the metal stress. Hence, the plants of the three annual arroach species or varieties used, all showed an intermediate level of tolerance according to the imposed treatments. The antioxidative activity seems to be of fundamental importance for adaptive responses of Atriplex plants against the metal toxicity. Abbreviations: SOD, superoxide dismutase; CAT, catalase; APX, ascorbate peroxidase; GR, glutathione reductase; GSH, reduced glutathione; GSSG, oxidized glutathione; ROS, reactive oxygen species; MDHA, monodehydroascorbate; NBT, nitroblue tetrazolium; POD, peroxidase.