Cadmium toxicity in plants

Abstract

Heavy metals are important environmental pollutants and their toxicity is a problem of increasing significance for ecological, evolutionary, nutritional, and environmental reasons. Plants posses homeostatic cellular mechanisms to regulate the concentration of metal ions inside the cell to minimize the potential damage that could result from the exposure to nonessential metal ions. This paper summarizes present knowledge in the field of higher plant responses to cadmium, an important environmental pollutant. Knowledge concerning metal toxicity, including mechanisms of cadmium homeostasis, uptake, transport and accumulation are evaluated. The role of the cell wall, the plasma membrane and the mycorrhizas, as the main barriers against cadmium entrance to the cell, as well as some aspects related to phytochelatin-based sequestration and compartmentalization processes are also reviewed. Cadmium-induced oxidative stress was also considered as one of the most studied topics of cadmium toxicity.

Oxidative Stress Induction by Lead in Leaves of Radish (Raphanus sativus) Seedlings

“…Despite being a non-redox metal, and thus not directly producing ROS (Benavides et al, 2005), Pb can interfere with antioxidant defense systems. Under stressful conditions the protective system can be over ridden by a rapid production of large amounts of ROS, leading to various structural modifications in proteins (Cargnelutti et al, 2006).…”

Tolerance and prospection of phytoremediator woody species of Cd, Pb, Cu and Cr

“…Plant tolerance and/or resistance to metallic stress can be associated with one or more mechanisms, such as: (i) the excretion of chelating compounds that reduce the availability of the metal in the soil or water; (ii) the exclusion of the metal through selective absorption of elements; (iii) the retention of the metal in roots, preventing its translocation to the aerial part; (iv) the chelation or sequestration of heavy metals by ligands, compartmentalization, biotransformation and mechanisms of cellular repair; (v) the development of enzymes tolerant to the metal (Hall, 2002;Cobbett and Goldsbrough, 2002;Patra et al, 2004); (vi) the increase of production of intracellular compounds linked to the metal (Sharma and Dietz, 2006); (vii) the immobilization of the metal in the cellular wall (Cosio et al, 2005); (viii) homeostatic cellular mechanisms to regulate the concentration of metal ions inside the cell (Benavides et al, 2005); (ix) induction of heat-shock proteins (Heckathorn et al, 2004); (x) release of phenols from roots (Jung et al, 2003); (xi) the increase of tolerance to mineral deficiency or the decrease of nutritional requirements; (xii) the increase in absorption of certain macronutrients; and (xiii) the development of the capacity to absorb and to use minerals in the presence of heavy metals (Meda et al, 2007). As a result of these tolerance and/or resistance mechanisms (alone or in combination), some plants can grow in environments contaminated with metals where other species do not survive (Hall, 2002).…”

Alleviating Effect of Exogenous Application of Ascorbic Acid on Growth and Mineral Nutrients in Cadmium Stressed Barley (Hordeum vulgare) Seedlings

“…Cadmium (Cd) is highly toxic, non-essential environmental pollutant found in air, water and soil (Sandalio et al, 2001;Benavides et al, 2005). One of the major sources of addition of Cd into agricultural soils is the application of phosphate fertilizers (Grant and Sheppard, 2008).…”