Arsenic Toxicity and Tolerance Mechanisms in Plants: An Overview

Abstract

Heavy metal stress is increasing at an alarming rate in agricultural soils through out the world. Heavy metal (Cd, Cu, Zn, Ni, Co, Cr, Pb and As) toxicity have been reported to be responsible for the reduced crop production. Among the heavy metals arsenic (As) is non-essential and toxic to both plants and animals. As can exist in environment in the form of oxidized arsenate (AsV) and reduced arsenite (AsIII). As stress has become a global concern, the uptake of As in the plants through contaminated soil will make its entry into the human food chain. As toxicity can lead to skin, bladder, lung and prostate cancer. Soil contaminated with As is the main source of arsenic in drinking water. Uptake of As by plants is very important in understanding its physiological effects and its metabolism within plants. How plants respond to the arsenic stress in plants is a major concern to biologists. As per the published literature numerous physiological processes are affected by the As toxicity. As is also responsible for oxidative stress in plants through the generation of reactive oxygen species (ROS) which attack the biomolecules like, membranes proteins, carbohydrates, nucleic acids etc. At the same time activity of enzymatic and non-enzymatic antioxidants are increased which helped the plant to withstand the toxicity of As. The present chapter throws light on the arsenic toxicity in plants and their tolerance mechanism in plants. The chapter also highlights the generation of reactive oxygen species and antioxidants during As stress.