摘要

The effects of increasing concentrations of cadmium (Cd) on the ultrastructure, Cd accumulation, nutrient elements contents, levels of chlorophyll pigments, hydrogen peroxide (H2O2), malondialdehyde (MDA), antioxidants, as well as the activities of antioxidant enzymes were investigated in the leaves of Hydrocharis dubia (Bl.) Backer. Cd exposure resulted in significant damage in chloroplasts and mitochondria, suggesting that Cd hastened the senescence of the tested plants. The accumulation of Cd was found to increase in a concentration dependent manner with a maximum of 1088 mu g g(-1) at 80 mu M. The levels of Ca, P and Cu declined and the levels of Mg increased under all Cd concentrations, but K and Fe contents increased initially and decreased thereafter. Pigment content decreased with the rise of the Cd concentrations. H2O2 content enhanced gradually at all Cd concentrations. MDA content increased progressively up to 60 mu M Cd, followed by a decline at higher concentration. The effect of Cd application on ascorbate (AsA) and reduced glutathione (GSH) contents was similar to that seen for H2O2 content. Peroxidase (POD) and catalase (CAT) activities first increased and then decreased, while superoxide dismutase (SOD) activity markedly decreased. Results suggest that Cd-induced oxidative damage in H. dubia is closely associated with the efficiency of its intrinsic antioxidant mechanisms, both the disorder of nutrient elements and the damage to the ultrastructure were indicative of general disarray in the cellular functions exerted by Cd.

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