Heavy Metal Tolerance in Crop Plants: Physiological and Biochemical Aspects

Plants are immobile and they have to adapt against adverse conditions of the environment for their survival. Heavy metal (HM) toxicity is posing a serious concern for the plant life and seriously hampering the food grain productivity. Heavy metals include the transition metals essential for plant nutrition as well as the nonessential elements. All these elements become toxic to crop plants when they are present at high tissue concentrations. Elevated concentration of HMs in soil may be due to natural as well as anthropogenic activities. Plants growing in HM-contaminated regions may accumulate a significant amount of these HMs. This paves a way for HMs to enter into food chain posing serious health concerns for animal and human life. A number of morphological, biochemical, and physiological alterations occur during HM toxicity including alteration in uptake mechanism and transportation of water, root and shoot growth, oxidative stress, and changes in HM complexing ligands for sequestration of these HMs into vacuole to reduce the HM concentration in cytoplasm. The present chapter deals with the physiological and biochemical responses of plants to HM toxicity along with shedding light on uptake and transport mechanisms of HMs in brief.