The effect of arsenic and sodium nitroprusside on the physiological responses and antioxidant enzymes activity of Isatis cappadocica

Arsenic (As) stress, through the creation of oxidative stress, can cause phytotoxicity (e.g. The decrease of growth and chlorophyll content) in plants. Nitric oxide (NO), by promotion of the antioxidant system, plays an important role in reducing heavy metal-induced oxidative stress. In this study, the role of exogenously applied sodium nitroprusside (SNP; a NO donor) on physiological responses and antioxidant enzymes activity of Isatis cappadocica were investigated to high levels of As. The results showed that, in the highest level of As, the oxidative damages increased and plant growth was reduced, while SNP alleviated these inhibitory effects. The maximum activity of antioxidant enzymes was observed at 1000 μM As treatment, in the presence of SNP. These results showed that the application of SNP, which is an activator of antioxidant enzymes, may play a compensatory role against As stress. In addition, the application of SNP can increase the antioxidant capacity of I. cappadocica against stress conditions. On the other side, the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX) and glutathione reductase (GR) were decreased at 1500 As treatment, where showed that Isatis possess low potential to suppress oxidative stress. Unlike other antioxidant enzymes, glutathione S-transferase (GST) activity under1500 As treatment has not only been reduced, but also increased. These results suggest that GST activity can play an important role in reducing the toxicity of high levels of As in I. cappadocica.