Page 112 - Plant-Based Remediation Processes

Chapter 6
Metal Remediation via In Vitro Root Cultures

Marı ´a del Socorro Santos-Dı ´az

6.1 Introduction

Some metals (Fe, Zn, Mn, Ni, Cu, and Mo) are essential for normal plant growth
and development since they are nutrients and/or constituents of many enzymes and
proteins. Nonessential heavy metals include As, Cd, Cr, Hg, Pb, Sb, and U.
However, elevated concentration of metals can be detrimental to living organisms.
They are toxic because they can replace metals in pigments or enzymes, disrupting
the function of these molecules (Manios et al. 2003; Hou et al. 2007; Jayakumare
et al. 2009). Heavy metals also cause oxidative stress, especially transition metals
such as Fe and Cu. The toxicity of heavy metals is generally ascribed to their high
affinity for nucleophilic groups. In fact, they are soft donors and will therefore
readily bind to soft acceptors such as sulphydryl groups (Stohs and Bagchi 1995;
Rivetta et al. 1997; Schutzendu ¨bel and Polle 2002).
Heavy metals are important environmental pollutants in soil, water, and air. Soil
pollution differs from air and water pollution, because metals persist in the soil for a
longer time than in other compartments of the biosphere (Lasat 2002). The main
sources of contamination are agricultural fertilizers, pesticides, burning of fossil
fuels, metalliferous mining, metallurgical industries, sewage sludge treatment,
municipal wastes, and electronic industries (Wei and Zhou 2008; Wu et al. 2010).
In addition to sites contaminated by human activity, other natural sources of heavy
metal pollution include the mineral deposits in many regions of the planet, volcanic
activity, and weathering of rocks (Carroll 1970; Hinkley et al. 2006).
There are around 430 plant species known, ranging from annual herbs to perennial
shrubs and trees, that accumulate metals in large amounts. These species are of
interest for potential use in phytoremediation of metal-contaminated environments

M.d.S. Santos-Dı ´az (*)
Faculty of Chemistry, University of San Luis Potosı ´, Manuel Nava 6, CP 78210 San Luis Potosı ´,
Mexico
e-mail: ssantos@uaslp.mx

D.K. Gupta (ed.), Plant-Based Remediation Processes, Soil Biology 35, 101
DOI 10.1007/978-3-642-35564-6_6, # Springer-Verlag Berlin Heidelberg 2013