In present study, growth, arsenic accumulation, and antioxidant responses in root of Isatis cappadocica were investigated in response to application of arsenate and phosphate. Reduction in root dry weights was significant with 1200 µM arsenate and 5 µM phosphate treatments. Phosphate had a steady effect on root dry weight improvement, especially in high arsenate treatments ≥ 200 μM. As concentrations in roots increased with increasing arsenate supply levels, and decreased markedly with increasing phosphate in each arsenate treatment.. Applied arsenate induced oxidative stress, which caused increasing the concentrations of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA). The activities of antioxidant enzyme such as catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) in Isatis cappadocica roots increased significantly from 200-800 µM arsenate and 5 µM phosphate treatments while their activities were decreased at 1200 µM arsenate and 5 µM phosphate, compared with control plants. The phosphate mediated decline of CAT, POD and APX activities, which could be an important factor in regulating As-induced oxidative stress in roots. Our results concluded that, I. cappadocica has a great capability to tolerance and accumulate the As . Also, application of phosphate has a clearly vital role in oxidative stress reduction in roots of exposed I. cappadocica to arsenate.

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