Cadmium Induced Oxidative Stress in Plants and Endogenous Ameliorative Mechanism – A Review

Environmental contamination with heavy metals, their uptake by edible plants, thereby placing the toxic metal in the food web, is a serious public health concern. Contamination of soil with heavy metals is a serious issue and quite alarming and may cause huge disturbances in the ecological balance and health of living creatures on earth. Increasing anthropogenic activities including mining and industrial growth, application of chemical fertilizers and waste disposal system have led to contamination to a toxic level. Cadmium is one of heavy metal pollutants for the soil and plants and is generally considered to be a highly toxic element with adverse effects on plant development and growth. Excess cadmium in soil reduces photosynthesis, and water and nutrient uptake. However, bioavailability and uptake of cadmium from soil by plant are influenced by several environmental factors including soil pH. Plants adopt different strategies to reduce Cd-induced oxidative damage. Enhanced activities of antioxidative enzymes increase tolerance of plants to stress. There are diverse strategies to avoid heavy metal toxicity. Immobilization of Cd by the cell wall and extracellular carbohydrates is the first barrier to prevent Cd stress at the root level. The present review discusses the principal sources of cadmium to plants, oxidative stress associated with uptake of cadmium from the soil by the plants and the in-built mechanism for reducing its uptake and detoxification.