Response of antioxidative enzymes to arsenic-induced phytotoxicity in leaves of a medicinal daisy, Wedelia chinensis Merrill

BACKGROUND: Wedelia chinensis Merrill (Asteraceae) is a medicinally important herb, grown abundantly in soils contaminated with heavy metals, including toxic metalloid arsenic (As). The leaves have immense significance in treatment of various ailments. OBJECTIVE: The present study was undertaken to ascertain whether the edible/usable parts experience oxidative stress in the form of membrane damage during As exposure or not. MATERIALS AND METHODS: Responses of seven antioxidant enzymes were studied in leaves under 20 mg/L of As treatment in pot experiment. RESULTS: When compared to control, activities of superoxide dismutase, monodehydroascorbatereductase, dehydroascorbatereductase, glutathione reductase, and gluathione peroxidase had increased, while the catalase level reduced and ascorbate peroxidase activity changed non-significantly in As-treated seedlings. This suggested overall positive response of antioxidant enzymes to As-induced oxidative stress. Although hydrogen peroxide content increased, level of lipid peroxidation and magnitude of membrane damage was quite normal, leading to normal growth (dry weight of shoot) of plant under Astreatment. CONCLUSION: W.chinensis is tolerant of As-toxicity, and thus, can be grown in As-contaminated zones.