Cadmium effects on mineral accumulation, antioxidant defence system and gas exchange in cucumber

The effects of different concentrations (10, 50, 100 and 500 mu M) of cadmium (Cd) on manganese (Mn) and iron (Fe), lipid peroxidation, activities of antioxidant enzymes and photosynthetic function were investigated in hydroponically grown cucumber (Cucumis sativus L.). Results indicated that cadmium was accumulated primarily in roots. In the roots and shoots, the cadmium content increased with the increasing cadmium concentrations, and induced decrease of manganese significantly (P < 0.005). The levels of iron had an increasing trend with increasing cadmium concentration and duration of treatment. Cadmium-induced oxidation stress and lipid peroxidation in C. sativus showed by the increased concentration of MDA (malondialdehyde). Cadmium induced higher SOD (superoxide dismutase) and POD (peroxidase) activities than CAT (catalase) activity, suggesting that SOD and POD provided a better defence mechanism against cadmium-induced oxidative damage in C. sativus. The net photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO2 concentration were reduced in the presence of cadmium.