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8 S. Chatterjee et al.

Fig. 1.2 Schematic representation of phytovolatilization where metals are volatilized by the
process of evapotranspiration by plants

contaminants. Phytovolatilization is very much promising for mercury (Hg) and
selenium (Se) in which metals are converted to a volatile form for release and
dilution into the atmosphere (Bhargava et al. 2012). This method is advantageous
over other phytoremediation methods as it removes metal(loid) from a site without
the need of harvest/disposal of contaminated plants (Fig. 1.2).

1.4.1 Detoxification of Mercury by Plants

The most spectacular achievements of biotechnology in phytoremediation were the
engineering of plants capable of removing methyl-Hg from contaminated soil
(Rugh et al. 1996; Brunner et al. 2008). The purpose is achieved by the introduction
of bacterial merA and merB genes into several plant species including Arabidopsis,
tobacco, poplar, rice, and cottonwood (Rugh et al. 1996; Bizily et al. 2000; Heaton
et al. 2003; Czako et al. 2006; Lyyra et al. 2007). The merA gene encodes an
NADPH-dependent mercuric ion reductase which converts Hg 2+ to nontoxic vola-
0
tile metallic Hg and merB encodes organomercurial lyase liberating Hg 2+ from
organomercurial compounds R-Hg + (Silver and Phung 2005). Transgenic A.
thaliana (Rugh et al. 1996; Yang et al. 2003), Nicotiana tabacum (Ruiz et al.