As, Cd, Cr, Cu, Hg: Physiological implications and toxicity in plants

Abstract

Plant heavy metal toxicity is a problem of global relevance and potential endangerment for every ecosystem. Factors determining the excess of toxic metals in environment are natural (mineralogy, geology, natural fluxes) and anthropogenic (burning, smelting, mining, industrialization). Some metals are essential to plants, but toxic in high concentrations, while others have no known biological functions and enter the plant cell based on their electrochemical similarity to some other essential metals. Diverse ways in which plants react to certain metal in excess define its tolerance or sensitivity. There are various ways in which excess metal concentrations induce toxicity, some of the most common being the breakdown of photosynthesis, impairment of gene regulation, and induction of reactive oxygen species (ROS) production. The objective of this chapter was to review some of the most important findings in the ways that presence of toxic levels of As, Cd, Cr, Cu, and Hg induces toxicity in plants, and the ways the plants react to such toxicity. The environmental relevance of each element is also reviewed.