Abstract

The responses of a medicine plant (Lonicera japonica Thunb.) to different cadmium (Cd) levels in the nutrient medium were studied. The results showed that the high Cd concentrations accumulated in roots and shoots of L. japonica, which increased ediblesecurity risk of the plant. The chlorophyll content showed slightly increase in plants exposed to 5 mg L^-1 Cd, but decreased exposed to higher Cd concentrations. The variation in chlorophyll content in plants in relation to Cd concentrations in medium is considered as a good biomarker for Cd stress. Elevated malondialdehyde (MDA) content in leaves and roots indicated the plants were subjected to Cd-induced oxidative stress. As a defensive mechanism, the cooperation of superoxide dismutases (SOD, EC 1.15.1.1), peroxidases (POD, EC 1.11.1.7) and catalases (CAT, EC 1.11.1.6) may play an important role in plant tolerance to Cd. These enzymes activity showed significant increase by exposure to low Cd concentrations, indicating some acclimation effect, but decrease by exposure to high Cd concentrations implicating a potential injury to the plant.

Key words: Antioxidant enzyme, growth, cadmium, Lonicera japonica Thunb., tolerance.