cadmium-induced stress and antioxidative responses in different brassica napus cultivars

to estimate plant resistance to cadmium chloride (cdcl2) stress for phytoremediation purposes, the effect of cadmium (cd) phytotoxicity was assessed on total soluble protein, chlorophyll (chl) content and antioxidant enzymes in the leaves of three different brassica napus (b. napus) cultivars; mohican, reg.cob and okapi. plants were exposed to three levels of cdcl2 (0.75, 1.5 and 2.25 mm) in irrigation water. a reduction in protein and chl content was noted for all treatments in the three cultivars. generally, superoxide dismutase (sod) and ascorbate peroxidase (apx) activities were increased with 0.75 mm cdcl2 and then decreased at higher concentrations. sod activity was enhanced up to 1.5 mm cdcl2 concentration in mohican cultivar. moreover, apx activity of okapi cultivar was increased at a much higher rate of cdcl2 levels compared to mohican and reg.cob cultivars. different concentrations of cdcl2 induced a reduction in the catalase (cat) activity of mohican and reg.cob. however, this activity was increased with 0.75 mm cdcl2 in okapi and then decreased with higher concentrations. these results indicate that b. napus cultivars have different tolerances to cdcl2 stress and in consequence, different phytoremediation efficiencies. moreover, because okapi possesses a higher antioxidant enzyme activity than the other two cultivars, it is suggested that it is probably the most tolerant cultivar to cdcl2 stress.