relocation of nutrients and altered plant–water relationship (Smith and Read 1997).
AM fungi in plant increase chlorophyll number in leaves, increased disease tolerance
capacity, tolerance against parasites, improved water stress mechanism and salinity,
and heavy metal toxicity (Bethlenfalvay 1992). AM fungi also help in the development of soil aggregates and soil conservation (Miller and Jastrow 1992). Assimilation and transfer of nitrogen from ammonium can also enhance biomass production
in soils with low nutrients (K, Ca, and Mg) (Liu et al. 2002). Role of VAM fungi was
shown in Fig. 6.3.
6.7 Role of VAM Fungi in Bioremediation
Mycorrhiza and plant show mutual relationship, and due to this, they help to
immobilize heavy metal. In this process, both plant and mycorrhiza play a vital
role in the removal of toxic metal and detoxification in plant cell as well as in VAM.
Mycorrhiza cannot survive without a plant; hence, mycorrhizal remediation techniques are also called modified form of phytoremediation that utilizes the advantage
derived from mycorrhizal fungi. In mycorrhizal remediation, some
phytoremediation techniques such as phytoextraction and phytostabilization were
utilized. Mycorrhizal remediation shows faster results as compared to
phytoremediation because fungal hyphae cover larger area (Gao et al. 2010).
Rufyikiria et al. (2004) recorded mycorrhizal remediation decrease transfer of
contaminants from roots to the shoots of plants. AM fungal spore can survive in
the soil up to 6 years (Nguyen et al. 2012); hence, they easily replicate and help in the
growth of any crop planted on the soil. Thus, mycorrhizal remediation certifies the
quick growth of vegetation on remediated soils.
6.7.1 Process of Detoxification
In different metabolic reactions, plants secrete chelating agents like histidine and
organic acids in soil. These chemicals bind to heavy metals, which are present in soil.
Plasma membrane has selective transportation capacity, as well as active and passive
transportation system; through transportation system, specific and nonspecific
metals are transported also from the pores of the plasma membrane (Fig. 6.4).
In intracellular detoxification, plant cells produced chelating agents like
phytochelatins and metallothionein which have high affinity for heavy metals.
Plant cells also secrete organic acids, amino acids, and specific metal chaperons.
These secretary molecules react with heavy metals and form a complex structure.
Heavy metal complex structures are exported from cytoplasm to tonoplast and then
finally to vacuole. Heavy metal complex compounds are stored in vacuole, inside
endoplasmic reticulum, and chloroplast (Briat and Lobreause 1997) (Fig. 6.5).
6 VAM: An Alternate Strategy for Bioremediation of Polluted Environment
165
AM fungi in plant increase chlorophyll number in leaves, increased disease tolerance
capacity, tolerance against parasites, improved water stress mechanism and salinity,
and heavy metal toxicity (Bethlenfalvay 1992). AM fungi also help in the development of soil aggregates and soil conservation (Miller and Jastrow 1992). Assimilation and transfer of nitrogen from ammonium can also enhance biomass production
in soils with low nutrients (K, Ca, and Mg) (Liu et al. 2002). Role of VAM fungi was
shown in Fig. 6.3.
6.7 Role of VAM Fungi in Bioremediation
Mycorrhiza and plant show mutual relationship, and due to this, they help to
immobilize heavy metal. In this process, both plant and mycorrhiza play a vital
role in the removal of toxic metal and detoxification in plant cell as well as in VAM.
Mycorrhiza cannot survive without a plant; hence, mycorrhizal remediation techniques are also called modified form of phytoremediation that utilizes the advantage
derived from mycorrhizal fungi. In mycorrhizal remediation, some
phytoremediation techniques such as phytoextraction and phytostabilization were
utilized. Mycorrhizal remediation shows faster results as compared to
phytoremediation because fungal hyphae cover larger area (Gao et al. 2010).
Rufyikiria et al. (2004) recorded mycorrhizal remediation decrease transfer of
contaminants from roots to the shoots of plants. AM fungal spore can survive in
the soil up to 6 years (Nguyen et al. 2012); hence, they easily replicate and help in the
growth of any crop planted on the soil. Thus, mycorrhizal remediation certifies the
quick growth of vegetation on remediated soils.
6.7.1 Process of Detoxification
In different metabolic reactions, plants secrete chelating agents like histidine and
organic acids in soil. These chemicals bind to heavy metals, which are present in soil.
Plasma membrane has selective transportation capacity, as well as active and passive
transportation system; through transportation system, specific and nonspecific
metals are transported also from the pores of the plasma membrane (Fig. 6.4).
In intracellular detoxification, plant cells produced chelating agents like
phytochelatins and metallothionein which have high affinity for heavy metals.
Plant cells also secrete organic acids, amino acids, and specific metal chaperons.
These secretary molecules react with heavy metals and form a complex structure.
Heavy metal complex structures are exported from cytoplasm to tonoplast and then
finally to vacuole. Heavy metal complex compounds are stored in vacuole, inside
endoplasmic reticulum, and chloroplast (Briat and Lobreause 1997) (Fig. 6.5).
6 VAM: An Alternate Strategy for Bioremediation of Polluted Environment
165