Cadmium-induced membrane lipid peroxidation and changes in antioxidant enzyme activities and peroxidase isoforms in Jerusalem artichoke seedlings.

Jerusalem artichoke (Helianthus tuberosus L.) seedlings cultured in sandy media were treated with Hoagland nutrition solution with different concentrations of Cd(NO(3))(2) from 0 to 400 micromol/L. After 50 days' treatment, Cd accumulation, activities of peroxidase (POD, EC 1.11.1.7), superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6) were measured and electrophoretograms of POD isoenzymes were analyzed. The accumulation of Cd in seedlings increased from Cd 50-100 micromol/L, after which further increases in Cd concentration resulted in only small increases in accumulation of Cd in seedlings. MDA content was markedly higher than control values indicating the enhanced membrane lipid peroxidation in roots and leaves. POD activities in leaf and root extracts increased with an increase of Cd concentration from 0 to 50 and 100 micromol/L and then decreased with further increases to 200 and 400 micromol/L. Under moderate Cd level of 50-200 micromol/L, SOD activities in leaf and root extracts increased whereas with a higher Cd level of 400 micromol/L marked inhibitions in enzyme activities were observed. With increase in Cd concentration marked elevations in CAT activities in leaves and roots were observed. Results of electrophoresis show that the alteration of POD isoenzyme was noticeable to Cd and an additional POD isoenzyme LP10 appeared. It is suggested that POD isoenzyme of Jerusalem artichoke seedlings could be used as bioindicator for soil contamination by Cd.