14.1 Introduction
Ecological rehabilitation of polluted soils is one of the major concerns in recent
decades due to human activities. Increase in pace of human activities are considered
as unprecedented threats to biosphere. Soil is one of the life-supporting factors of this
planet but continued industrialization, urbanization, intense agricultural practices,
etc. are degrading the quality of the land. More than 30% of the land has been
degraded by various anthropogenic activities (Abhilash et al. 2012; Ma et al. 2011a).
Pollution, salinity stress, soil erosion, etc. are the processes which deteriorate the soil
properties. Large numbers of chemicals like pesticides, heavy metals, persistent
organic pollutants, chlorinated solvents, etc. have been detected from soil, water,
and air. These discharged entities alter the ecosystem balance that would ultimately
deteriorate the quality of food and affect human health (Sivarajasekar and Baskar
2015a, b; Muthusaravanan et al. 2018). They have been documented to cause serious
health hazards which include cancer, kidney malfunctioning, impaired central nervous system, skin problems, weakening of bones, etc. (Jarup 2003). Emamverdian
et al. (2015) in his study reported oxidative stress in rice seedlings grown in the
presence of heavy metals. Similar reports have been reported by many researchers on
the generation of oxidative stress under various heavy metals (Pb, Cd, Cr, etc.)
(Kohli et al. 2018; Kaur et al. 2018). Plants itself have innate defense response to
thrive in stressed environment which includes immobilization, chelation, vacuolar
sequestration, expression of defense-related genes, and metal transporters (Sharma
et al. 2019; Khanna et al. 2019; Bali et al. 2019). But due to overexploitation of
resources, these contaminants are gaining momentum and are considered as challenging mission due to their persistent nature in the ecosystem. Contaminated lands
show direct and indirect effect on social, economic, and environmental half of the
society. Conventional cleanup methods like physicochemical methods are very
costly and laborious.
Bioremediation is an ecofriendly process in which living organisms are used to
get rid of various contaminants present in the soil (Abhilash et al. 2009). There is an
increasing demand for utilization of plants and their microflora for remediation of
contaminated soils which proves to be effective and cost-friendly. Several plant
species have potential to remediate the contaminated soil like Brassica, castor, Salix,
Populus, etc. (Kohli et al. 2018; Huang et al. 2011; Pulford and Watson 2003). The
indirect benefits of growing plants in contaminated sites such as improvement in soil
quality, biofuel production, carbon sequestration, biodiversity balance, and aesthetic
value have been studied by Abhilash et al. (2019). Phytoremediation potential of the
contaminated soil depends upon the extent of contaminants present in the soil,
edaphic factors such as biotic diversity of the soil, organic matter, pH, plant-soilwater interaction, availability of nutrients, etc. (Weyens et al. 2009). Plant
microbiota which includes plant growth-promoting rhizobacterias (PGPRs), earthworm, fungi, actinomycetes, etc. plays an effective role in the remediation of
contaminated sites.
228
P. Sharma et al.
Ecological rehabilitation of polluted soils is one of the major concerns in recent
decades due to human activities. Increase in pace of human activities are considered
as unprecedented threats to biosphere. Soil is one of the life-supporting factors of this
planet but continued industrialization, urbanization, intense agricultural practices,
etc. are degrading the quality of the land. More than 30% of the land has been
degraded by various anthropogenic activities (Abhilash et al. 2012; Ma et al. 2011a).
Pollution, salinity stress, soil erosion, etc. are the processes which deteriorate the soil
properties. Large numbers of chemicals like pesticides, heavy metals, persistent
organic pollutants, chlorinated solvents, etc. have been detected from soil, water,
and air. These discharged entities alter the ecosystem balance that would ultimately
deteriorate the quality of food and affect human health (Sivarajasekar and Baskar
2015a, b; Muthusaravanan et al. 2018). They have been documented to cause serious
health hazards which include cancer, kidney malfunctioning, impaired central nervous system, skin problems, weakening of bones, etc. (Jarup 2003). Emamverdian
et al. (2015) in his study reported oxidative stress in rice seedlings grown in the
presence of heavy metals. Similar reports have been reported by many researchers on
the generation of oxidative stress under various heavy metals (Pb, Cd, Cr, etc.)
(Kohli et al. 2018; Kaur et al. 2018). Plants itself have innate defense response to
thrive in stressed environment which includes immobilization, chelation, vacuolar
sequestration, expression of defense-related genes, and metal transporters (Sharma
et al. 2019; Khanna et al. 2019; Bali et al. 2019). But due to overexploitation of
resources, these contaminants are gaining momentum and are considered as challenging mission due to their persistent nature in the ecosystem. Contaminated lands
show direct and indirect effect on social, economic, and environmental half of the
society. Conventional cleanup methods like physicochemical methods are very
costly and laborious.
Bioremediation is an ecofriendly process in which living organisms are used to
get rid of various contaminants present in the soil (Abhilash et al. 2009). There is an
increasing demand for utilization of plants and their microflora for remediation of
contaminated soils which proves to be effective and cost-friendly. Several plant
species have potential to remediate the contaminated soil like Brassica, castor, Salix,
Populus, etc. (Kohli et al. 2018; Huang et al. 2011; Pulford and Watson 2003). The
indirect benefits of growing plants in contaminated sites such as improvement in soil
quality, biofuel production, carbon sequestration, biodiversity balance, and aesthetic
value have been studied by Abhilash et al. (2019). Phytoremediation potential of the
contaminated soil depends upon the extent of contaminants present in the soil,
edaphic factors such as biotic diversity of the soil, organic matter, pH, plant-soilwater interaction, availability of nutrients, etc. (Weyens et al. 2009). Plant
microbiota which includes plant growth-promoting rhizobacterias (PGPRs), earthworm, fungi, actinomycetes, etc. plays an effective role in the remediation of
contaminated sites.
228
P. Sharma et al.