Journal of Environmental Biology

Antioxidative response of Lemna polyrrhiza L. to cadmium stress

Riffat John¹, Parvaiz Ahmad², Kasturi Gadgil¹ and Satyawati Sharma*²

*satyawatis@hotmail.com

¹Centre for Energy Studies, Indian Institute of Technology Delhi, Hauz Khas, New Delhi-110 016, India

²Centre for Rural Development and Technology, Indian Institute of Technology Delhi, Hauz Khas, New Delhi-110 016, India

(Received: March 9, 2005 ; Revised received: July 5, 2005 ; Accepted: August 18, 2005)

Abstract: Growth, lipid peroxidation, different antioxidative enzymes and metal accumulation were studied in  Lemna polyrrhiza treated with different concentrations (1-40 ppm) of CdSO₄. The growth of the plant was slightly enhanced with 1 ppm, while higher concentrations retarted growth and multiplication of fronds, the effect being concentration and dose dependant. Increase in malondialdehyde content was insignificant after the first week but a prolonged exposure led to significant (p<0.05) increase of about 38% and 45% over the control in 20 and 30 ppm, respectively, after four weeks. Catalase (EC 1.11.1.6; CAT) activity increased at low concentration, but it declined to 42% and 54% at 40 ppm after 6 and 30 days, respectively. Superoxide dismutase (EC 1.15.1.1; SOD), ascorbate peroxidase (EC 1.11.1.11; APx) and glutathione reductase (EC 1.6.4.2) increased at both low as well at high concentrations, but a prolonged exposure to high concentration of Cd (40 ppm) led to significant (p<0.05) decline in the mean activities of these antioxidant enzymes. Accumulation of Cd in biomass was concentration and time dependant. However at high concentration of 40 ppm, Cd accumulation did not increase significantly (p<0.05) with time. Increased activities of antioxidant enzymes in Cd treated plants suggest that metal tolerance in L. polyrrhiza  might be associated to the changes of antioxidant enzymatic activities.

Key words:   Antioxidant enzymes, CAT, SOD, APx, Cd, Lemna polyrrhiza

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