increased 100–250 mgCo/kg, plants show lower nutrient contents. Similar results
were observed in radish and mung bean, when 50 mgCo/kg of heavy metal present in
soil increase plant growth as well as physiochemical properties, whereas reductions
were recorded at 100–250 mgCo/kg of heavy metal present in soil concentration
(Jayakumar et al. 2008, 2007). Enhancement in growth of cluster beans has also been
reported at lower (25 mg/L) Zn concentration of the soil solution, and opposite
results were observed when the concentration of Zn (50 mg Zn/L) was increased
(Manivasagaperumal et al. 2011). Nicholls and Mal (2003) reported that the mixture
of Pb and Cu at high (1000 mg/kg each) and low (500 mg/kg) concentrations
resulted in a rapid and complete death of the leaves and stem of Lythrum salicaria.
Some related data are shown in Table 6.1.
6.1.2 Effect of Various Heavy Metals on Fungi
Heavy metals can alter major mechanisms of fungi. Due to metal toxic effect, many
biological important molecules were unfunctional, for example, reaction of enzyme,
transfer of nutrients and ions, the dislocation and/or exchange of essential metal ions,
structural change, denaturation and inactivation of biomolecule, and interruption of
cell function and organellar membrane integrity (Ochiai 1987). Fungi and metal
show broad spectrum toxic interaction at every aspect of metabolism, development,
and differentiation may be affected, depending on the individual, types of metal,
concentration, and soil properties (Ross 1975; Gadd 1986; Gadd and White 1989).
We all know that heavy metals are essential for the cultivation of filamentous fungi
on synthetic media. Fungal continuous existence generally depends on different
characteristics: biochemical and structural properties, physiological and/or genetical
adaptation, morphological changes, and environmental alteration, availability, and
toxicity (Gadd and Griffiths 1978; Gadd 1992a). Metal resistance is a word which
means organisms have the ability to grow in the presence of metal by means of a
mechanism produced in direct response to the metal species consumed, e.g.,
metallothionein or γ-glutamyl peptide synthesis (Mehra and Winge 1991). “Metal
tolerance” depends on intrinsic properties and/or environmental modification of
toxic metal (Gadd 1992b, c, 1993). Intrinsic properties include permeability of cell
walls, extracellular biomolecule (polysaccharide), and secretion of metabolite,
which help in detoxification of the metal species by binding or precipitation.
However, distinctions are complicated in many cases because of the participation
of several direct and indirect physico-chemical and biological mechanisms in survival. Biological mechanisms are altered (including extracellular precipitation, complexation and crystallization, transformation of metal species by oxidation,
reduction, methylation, and dealkylation, biosorption to cell walls, pigments, and
extracellular toxicity) for fungal survival (as distinct from environmental modification of toxicity). Some related data are shown in Table 6.2.
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P. Verma et al.
were observed in radish and mung bean, when 50 mgCo/kg of heavy metal present in
soil increase plant growth as well as physiochemical properties, whereas reductions
were recorded at 100–250 mgCo/kg of heavy metal present in soil concentration
(Jayakumar et al. 2008, 2007). Enhancement in growth of cluster beans has also been
reported at lower (25 mg/L) Zn concentration of the soil solution, and opposite
results were observed when the concentration of Zn (50 mg Zn/L) was increased
(Manivasagaperumal et al. 2011). Nicholls and Mal (2003) reported that the mixture
of Pb and Cu at high (1000 mg/kg each) and low (500 mg/kg) concentrations
resulted in a rapid and complete death of the leaves and stem of Lythrum salicaria.
Some related data are shown in Table 6.1.
6.1.2 Effect of Various Heavy Metals on Fungi
Heavy metals can alter major mechanisms of fungi. Due to metal toxic effect, many
biological important molecules were unfunctional, for example, reaction of enzyme,
transfer of nutrients and ions, the dislocation and/or exchange of essential metal ions,
structural change, denaturation and inactivation of biomolecule, and interruption of
cell function and organellar membrane integrity (Ochiai 1987). Fungi and metal
show broad spectrum toxic interaction at every aspect of metabolism, development,
and differentiation may be affected, depending on the individual, types of metal,
concentration, and soil properties (Ross 1975; Gadd 1986; Gadd and White 1989).
We all know that heavy metals are essential for the cultivation of filamentous fungi
on synthetic media. Fungal continuous existence generally depends on different
characteristics: biochemical and structural properties, physiological and/or genetical
adaptation, morphological changes, and environmental alteration, availability, and
toxicity (Gadd and Griffiths 1978; Gadd 1992a). Metal resistance is a word which
means organisms have the ability to grow in the presence of metal by means of a
mechanism produced in direct response to the metal species consumed, e.g.,
metallothionein or γ-glutamyl peptide synthesis (Mehra and Winge 1991). “Metal
tolerance” depends on intrinsic properties and/or environmental modification of
toxic metal (Gadd 1992b, c, 1993). Intrinsic properties include permeability of cell
walls, extracellular biomolecule (polysaccharide), and secretion of metabolite,
which help in detoxification of the metal species by binding or precipitation.
However, distinctions are complicated in many cases because of the participation
of several direct and indirect physico-chemical and biological mechanisms in survival. Biological mechanisms are altered (including extracellular precipitation, complexation and crystallization, transformation of metal species by oxidation,
reduction, methylation, and dealkylation, biosorption to cell walls, pigments, and
extracellular toxicity) for fungal survival (as distinct from environmental modification of toxicity). Some related data are shown in Table 6.2.
156
P. Verma et al.