Antioxidative response appraisal of callus cultures of Solanum lycopersicum L. under heavy metal stress

Heavy metal stress can adversely affect crop productivity by retarding its growth. Among different heavy metals, copper (Cu) and nickel (Ni) are micronutrients for plants however, they can act as major pollutants when present at concentrations beyond permissible limits. Lead (Pb) is another pollutant which is not an essential element for plants but it gets easily absorbed and accumulated in different plant parts. Solanum lycopersicum L. (tomato) is a major source of antioxidants like lycopene, vitamin C, folate, vitamin K and potassium which have been linked to many health benefits. Keeping in mind the economic significance of S. lycopersicum and at the same time toxicity of copper, nickel and lead, the present work was carried out to determine uptake of Cu, Ni and Pb by callus cultures of tomato upon exposure to different concentrations (50–500 µM) of these metals. In addition, protein content and activities of different antioxidant enzymes such as catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), peroxidase (POD), glutathione S transferase (GST) and superoxide dismutase (SOD) were also determined in tomato callus cultures. A dose dependent increase in metal uptake, protein content and antioxidative enzyme activities was observed in callus cultures of tomato treated with increasing concentrations of Cu, Ni and Pb metals while the activity of SOD was noticed to be decreased.