Cadmium-induced stress on the seed germination and seedling growth of Brassica napus L., and its alleviation through exogenous plant growth regulators

Because of its prolific growth, oilseed rape (Brassica napus L.) can be grown advantageously for phytoremediation of the lands contaminated by industrial wastes. Therefore, toxic effect of cadmium on the germination of oilseed rape, the capability of plants for cadmium phytoextraction, and the effect of exogenous application of plant growth regulators to mitigate phytotoxicity of cadmium were investigated. For the lab study of seedlings at early stage, seeds were grown on filter papers soaked in different solutions of Cd2+ (0, 10, 50, 100, 200 and 400 mu M). In greenhouse study, seedlings were grown in soil for 8 weeks, transferred to hydroponic pots for another 6 weeks growth, and then treated with plant growth regulators and cadmium. Four plant growth regulators viz. jasmonic acid (12.5 mu M), abscisic acid (10 mu M), gibberellin (50 mu M) and salicylic acid (50 mu M); and three levels of Cd2+ (0, 50 and 100 mu M) were applied. Data indicated that lower concentration of Cd2+ (10 mu M) promoted the root growth, whereas the severe stresses (200 or 400 mu M) had negative effect on the establishment of germinating seedlings. Plants treated with any of the tested plant growth regulators alleviated cadmium toxicity symptoms, which were reflected by more fresh weight, less malondialdehyde concentration in leaves and lower antioxidant enzyme activities. The application of abscisic acid to the plants cultivated in the medium containing 100 mu M Cd2+ resulted in significantly lower plant internal cadmium accumulation.