very efficient in remediating toxic metals and metalloids of affected ecosystems
(Dhankher et al. 2011). Figure 4.1 depicts the achievement of improved tolerance
and metal accumulation by plants through genetic modification in metal transporters.
A few reports showed the engineering of yeast cadmium factor (YCF1)
overexpression in the plant Arabidopsis thaliana improved tolerance to HMs such
as Cd(II) and PB(II); the plants even started accumulating HMs higher in their
vacuoles followed by the conjugating glutathione (GSH) (Crowley et al. 1991;
Song et al. 2003). Although we can clearly understand many of the soil–microbe–
plant interactions in uptake, translocation, and accumulation of different types of
heavy metals in their system, the fate of metals and the biological mechanisms
underlying the methods of plant decontamination procedures are poorly understood,
presenting a limiting factor that seeks our further attention.
6.2 Enhancing Metals and Metalloids Ligand Production
The variety of plant species and the type of metal contaminant decide the uptake and
translocation of metals from roots to shoots of the plants. Differences in metal
mobility are noted inside the plant system; when compared with Cu and Pb, metals
such as Cd and Zn had more mobility inside the plants. During transport, many of the
metals started to bind to the cell walls of plant roots, leading to their higher
accumulation. So, to overcome this, chelation ligands such as organic and amino
acids and thiols are important in facilitating their movement to the aboveground
levels of plants, thus increasing remediating efficiency (Grill et al. 1987; Zacchini
et al. 2009). Xylem cells have a high capability of cationic exchange, resulting in
retreat of metal movement inside the shoot if not ligand chelated.
6.3 Rhizoremediation: The Combinatorial Effects of Bioand Phytoremediation
Rhizosphere microorganisms are exploited for use in remediating polluted environments, referred to as rhizoremediation, the combined approach of bioaugmentation
and phytoremediation. Rhizoremediation laid a platform for engineering more than
one microbial culture for desired factors of remediating a mixed type of pollutants in
the co-contaminated substrate, which has attracted research (Khan 2006); especially,
the bacterial communities draw much attraction for easy engineering effects in
remediating different pollutants of co-contaminant sites (Wu et al. 2006; Yang
et al. 2009). It was reported that the selection of the organism to be used is very
important for successful rhizoremediation. Different varieties of grass and many of
the leguminous plants such as alfalfa were found to be suitable plants for
rhizoremediation (Kuiper et al. 2001; Qiu et al. 1994; Gupta and Sandallo 2011).
96
M. K. Awasthi et al.
(Dhankher et al. 2011). Figure 4.1 depicts the achievement of improved tolerance
and metal accumulation by plants through genetic modification in metal transporters.
A few reports showed the engineering of yeast cadmium factor (YCF1)
overexpression in the plant Arabidopsis thaliana improved tolerance to HMs such
as Cd(II) and PB(II); the plants even started accumulating HMs higher in their
vacuoles followed by the conjugating glutathione (GSH) (Crowley et al. 1991;
Song et al. 2003). Although we can clearly understand many of the soil–microbe–
plant interactions in uptake, translocation, and accumulation of different types of
heavy metals in their system, the fate of metals and the biological mechanisms
underlying the methods of plant decontamination procedures are poorly understood,
presenting a limiting factor that seeks our further attention.
6.2 Enhancing Metals and Metalloids Ligand Production
The variety of plant species and the type of metal contaminant decide the uptake and
translocation of metals from roots to shoots of the plants. Differences in metal
mobility are noted inside the plant system; when compared with Cu and Pb, metals
such as Cd and Zn had more mobility inside the plants. During transport, many of the
metals started to bind to the cell walls of plant roots, leading to their higher
accumulation. So, to overcome this, chelation ligands such as organic and amino
acids and thiols are important in facilitating their movement to the aboveground
levels of plants, thus increasing remediating efficiency (Grill et al. 1987; Zacchini
et al. 2009). Xylem cells have a high capability of cationic exchange, resulting in
retreat of metal movement inside the shoot if not ligand chelated.
6.3 Rhizoremediation: The Combinatorial Effects of Bioand Phytoremediation
Rhizosphere microorganisms are exploited for use in remediating polluted environments, referred to as rhizoremediation, the combined approach of bioaugmentation
and phytoremediation. Rhizoremediation laid a platform for engineering more than
one microbial culture for desired factors of remediating a mixed type of pollutants in
the co-contaminated substrate, which has attracted research (Khan 2006); especially,
the bacterial communities draw much attraction for easy engineering effects in
remediating different pollutants of co-contaminant sites (Wu et al. 2006; Yang
et al. 2009). It was reported that the selection of the organism to be used is very
important for successful rhizoremediation. Different varieties of grass and many of
the leguminous plants such as alfalfa were found to be suitable plants for
rhizoremediation (Kuiper et al. 2001; Qiu et al. 1994; Gupta and Sandallo 2011).
96
M. K. Awasthi et al.