1 Introduction
The stages of environmental contamination by the use of pesticides, heavy metals
(HMs), leather tannery effluents, phenols, organic matter, explosives, azo dyes
have increased significantly over the last few decades, mostly due to industries and
tanneries (Perotti et al. 2020). Tannery effluents contain large quantities of both
inorganic and organic contaminants, such as phenols and hexavalent chromium
(Cr (VI)). It is well known that toxicity depends upon the redox state. In the case of
chromium, for example, Cr (VI) is highly toxic compared to Cr (III) due to its high
solubility, availability, and mobility in the soil as well as through biological
membranes. Based on the facts, the removal of toxic compounds from the environment is of high relevance for a safe environment. In this sense, many biological
methods have been proposed to remove these harmful substances from the water
bodies and soil (Chen et al. 2012). Phytoremediation, using plant vegetation to
degrade the contaminated environments, is a green and eco-friendly technology
that has gained importance concerning traditional decontamination methods
(Flocco and Giulietti 2007).
In recent decades, a research area in the area of phytoremediation experienced
increasing interest, mainly in Europe and the United States, but also in developing
countries. Even though it was primarily implemented for the degradation of different
kinds of inorganic impurities from soil samples, the phytoremediation approach has
increasingly proving to be proficient for the processing of organic contaminants
additionally. These facts are making it necessary to acquire discernment into the
machinery essential for the decontamination process. Prior to the implementation of
a phytoremediation protocol to field conditions, it is necessary to conduct laboratoryscale studies, for which the plant experimental models systems are essential. These
model systems permit the control and reproducibility in experimental conditions
necessary for conducting basic phytoremediation research.
In vitro plant cultures especially hairy root cultures (HRCs) are a useful alternative methodology for decontamination of PCBs, trinitrotoluene (TNT), textile dyes,
phenolics, HMs, and radioactive nuclides (Agostini et al. 2013). Hairy roots (HRs)
are originated by the infection of explants with Agrobacterium rhizogenes strain,
gram-negative soil bacteria by transfers of the transfer DNA comprising the loci
between the T R and T L region of the root-inducing plasmid (Chandra 2012; Lal
2020; Sujatha et al. 2013). Concomitantly, as the genetic and biochemical properties
of HRs were exposed, scientific community started focussing on its exploitation for
research benefits. The main reason behind this is the major property that has attracted
scientists the most was the equal or sometimes higher potential of HRs to produce
important bioactive compounds, and the HRs biotechnology podium has proved to
be valuable systems for studying key aspects of pollutants phytoremediation
(Georgiev et al. 2012). Even plant root cultures also provoke the breakdown of
harmful substances in the soils through the secretion of root exudates and oxidoreductive enzymes that are mainly involved in the degradation of organic pollutants
(Jha et al. 2020).
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A. K. Moola et al.
The stages of environmental contamination by the use of pesticides, heavy metals
(HMs), leather tannery effluents, phenols, organic matter, explosives, azo dyes
have increased significantly over the last few decades, mostly due to industries and
tanneries (Perotti et al. 2020). Tannery effluents contain large quantities of both
inorganic and organic contaminants, such as phenols and hexavalent chromium
(Cr (VI)). It is well known that toxicity depends upon the redox state. In the case of
chromium, for example, Cr (VI) is highly toxic compared to Cr (III) due to its high
solubility, availability, and mobility in the soil as well as through biological
membranes. Based on the facts, the removal of toxic compounds from the environment is of high relevance for a safe environment. In this sense, many biological
methods have been proposed to remove these harmful substances from the water
bodies and soil (Chen et al. 2012). Phytoremediation, using plant vegetation to
degrade the contaminated environments, is a green and eco-friendly technology
that has gained importance concerning traditional decontamination methods
(Flocco and Giulietti 2007).
In recent decades, a research area in the area of phytoremediation experienced
increasing interest, mainly in Europe and the United States, but also in developing
countries. Even though it was primarily implemented for the degradation of different
kinds of inorganic impurities from soil samples, the phytoremediation approach has
increasingly proving to be proficient for the processing of organic contaminants
additionally. These facts are making it necessary to acquire discernment into the
machinery essential for the decontamination process. Prior to the implementation of
a phytoremediation protocol to field conditions, it is necessary to conduct laboratoryscale studies, for which the plant experimental models systems are essential. These
model systems permit the control and reproducibility in experimental conditions
necessary for conducting basic phytoremediation research.
In vitro plant cultures especially hairy root cultures (HRCs) are a useful alternative methodology for decontamination of PCBs, trinitrotoluene (TNT), textile dyes,
phenolics, HMs, and radioactive nuclides (Agostini et al. 2013). Hairy roots (HRs)
are originated by the infection of explants with Agrobacterium rhizogenes strain,
gram-negative soil bacteria by transfers of the transfer DNA comprising the loci
between the T R and T L region of the root-inducing plasmid (Chandra 2012; Lal
2020; Sujatha et al. 2013). Concomitantly, as the genetic and biochemical properties
of HRs were exposed, scientific community started focussing on its exploitation for
research benefits. The main reason behind this is the major property that has attracted
scientists the most was the equal or sometimes higher potential of HRs to produce
important bioactive compounds, and the HRs biotechnology podium has proved to
be valuable systems for studying key aspects of pollutants phytoremediation
(Georgiev et al. 2012). Even plant root cultures also provoke the breakdown of
harmful substances in the soils through the secretion of root exudates and oxidoreductive enzymes that are mainly involved in the degradation of organic pollutants
(Jha et al. 2020).
30
A. K. Moola et al.