110
C. Dileep et al.
All the siderophores in this family are related by having a cyclic or linear peptide
containing D- and L- amino acids, mixed ligand groups with at least one hydroxamate
group or and a-hydroxy acid. Structurally at least eight amino acid residues are
required for cyclic compounds. Even different strains of the same organism produce
different pseudobactins which are discriminated in the uptake process of the various
strains. The affinity of siderophores for Fe
3+ is expressed as a binding or stability
constant log 10 K Fe (pH 7.0). It is pH-dependent, varies widely among the various
siderophores, and is thus an important ecological factor in the microbial competition
for iron.
The solubility of organic iron might be relative to the soil type (Benjamini and
Hochberg 1995). Iron is more soluble and biologically available at low pH (Wandersman and Delepelware 2004). Increasing pH siderophore production ceased, this
may be since alkaline pH help in excess solubilization of iron, which increases
the iron content of the soil. Acidity affects metal speciation and bio-availability to
microbes through various mechanisms (Lofts et al. 2004; Gobran and Huang 2011).
P. aeruginosa species from acidic soil shows siderophore production in iron-deficient
succinate medium in varying degree of absorbance and peaks. A potent siderophore,
such as the ferric-siderophore complex plays an important role in iron uptake by
plants in the presence of other metals, such as nickel and cadmium (Beneduzi et al.
2012).
5.5 Plant Responses to Salinity
The ability of the plant to the saline environment depends on its genetic makeup and
physiological responses. Cereals and vegetables are very sensitive to salinity (Paul
and Lade 2014). Plant response to salinity starts by the osmotic adjustments and later
by the specific ion effects. High salinity causes structural and functional impairments
in plants and affects crop productivity (Meng et al. 2017). Plants exposed to salinity
show stunted growth, delay or absence of germination, low seedling growth, decrease
in root length, and root meristems (Ameixa et al. 2016; Konuskan et al. 2017; Taibi
et al. 2016; Acosta-Motos et al. 2017). Salt stress creates nutrient imbalances (Grattan
and Grieve 1998). Physiological responses to salinity results in the reduction of crop
production by altering the protein synthesis, photosynthesis (Pessarakli 2014).
5.6 Unavailability of Iron in Saline Soils
Limited iron availability in soil is one of the leading causes of a reduction in crop
productivity. Iron is playing a key role in photosynthesis, electron transport, enzymatic processes involving oxygen (Ferreira et al. 2019). Iron catalysis the chlorophyll
synthesis (Hu et al. 2017) and is the second most abundant metal in the earth’s crust;
rather it is not accessible to plants. This is due to the insolubility of Iron. Fe
2+ and
C. Dileep et al.
All the siderophores in this family are related by having a cyclic or linear peptide
containing D- and L- amino acids, mixed ligand groups with at least one hydroxamate
group or and a-hydroxy acid. Structurally at least eight amino acid residues are
required for cyclic compounds. Even different strains of the same organism produce
different pseudobactins which are discriminated in the uptake process of the various
strains. The affinity of siderophores for Fe
3+ is expressed as a binding or stability
constant log 10 K Fe (pH 7.0). It is pH-dependent, varies widely among the various
siderophores, and is thus an important ecological factor in the microbial competition
for iron.
The solubility of organic iron might be relative to the soil type (Benjamini and
Hochberg 1995). Iron is more soluble and biologically available at low pH (Wandersman and Delepelware 2004). Increasing pH siderophore production ceased, this
may be since alkaline pH help in excess solubilization of iron, which increases
the iron content of the soil. Acidity affects metal speciation and bio-availability to
microbes through various mechanisms (Lofts et al. 2004; Gobran and Huang 2011).
P. aeruginosa species from acidic soil shows siderophore production in iron-deficient
succinate medium in varying degree of absorbance and peaks. A potent siderophore,
such as the ferric-siderophore complex plays an important role in iron uptake by
plants in the presence of other metals, such as nickel and cadmium (Beneduzi et al.
2012).
5.5 Plant Responses to Salinity
The ability of the plant to the saline environment depends on its genetic makeup and
physiological responses. Cereals and vegetables are very sensitive to salinity (Paul
and Lade 2014). Plant response to salinity starts by the osmotic adjustments and later
by the specific ion effects. High salinity causes structural and functional impairments
in plants and affects crop productivity (Meng et al. 2017). Plants exposed to salinity
show stunted growth, delay or absence of germination, low seedling growth, decrease
in root length, and root meristems (Ameixa et al. 2016; Konuskan et al. 2017; Taibi
et al. 2016; Acosta-Motos et al. 2017). Salt stress creates nutrient imbalances (Grattan
and Grieve 1998). Physiological responses to salinity results in the reduction of crop
production by altering the protein synthesis, photosynthesis (Pessarakli 2014).
5.6 Unavailability of Iron in Saline Soils
Limited iron availability in soil is one of the leading causes of a reduction in crop
productivity. Iron is playing a key role in photosynthesis, electron transport, enzymatic processes involving oxygen (Ferreira et al. 2019). Iron catalysis the chlorophyll
synthesis (Hu et al. 2017) and is the second most abundant metal in the earth’s crust;
rather it is not accessible to plants. This is due to the insolubility of Iron. Fe
2+ and