Heavy Metal Toxicity and Tolerance in Crop Plants

Heavy metal–contaminated soils pose a major environmental challenge. Soils are contaminated with heavy metals due to industrial, agricultural and human activities. Heavy metal contamination can cause dysfunction in biodiversity by reducing soil fertility and microbial activity. Heavy metals are persistent in nature and cannot be removed by biological processes, but can be transformed from one chemical form to another. Toxicity of metals can cause physiological changes, such as decrease in water potential, increased production of ROS, enzyme inhibition, oxidation of nucleic acids and proteins, cell death and developmental changes such as growth inhibition. Exposure to toxic levels of heavy metals can trigger stress response and adaptation at physiological, developmental, structural and molecular levels. Agricultural soils affected with heavy metal toxicity need special consideration because heavy metals have the potential to accumulate in crop plants, which can affect all trophic levels. There is a critical need for reliable bioassays for risk assessment of heavy metal toxicity in plant systems. In this chapter, transport of heavy metals, their effect on plant metabolism and sequestration have been discussed.