Copper accumulation, localization and antioxidant response in Eclipta alba L. in relation to quantitative variation of the metal in soil

Eclipta alba L. is a well known medicinal herb, found commonly on contaminated roadsides in Kerala, India. To assess its potential for copper tolerance and accumulation, pot culture experiment was carried out. Metal accumulation in the plant in relation to 50-800 mg kg(-1) Cu in soils, administered as CuSO4 center dot 7H(2)O in solution, was examined. Biomass yield of shoot and root, pigment content, Cu accumulation in the plant, bio-concentration factor, and translocation factor were the parameters studied. At the highest level of treatment, Cu was found accumulated more in the roots than in shoots. A significant increase in lipid peroxidation, proline content, phenolics and flavanoids were observed in Cu treated plants, compared to the control. The activity of antioxidant enzymes like superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase was found significantly changed in all the treated plants than in the control. The Bradford assay revealed a significant increase in protein content of the plant at higher levels of Cu treatment. Transmission electron microscopy, images supported the uptake and sequestration of metal particles inside the plant cell. The overall data suggests Eclipta alba L. to be a plant with high potential to tolerate Cu toxicity in soil.