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G. Garg et al.
five groups, depending on their side chain group hydroxamate (Renshaw et al. 2002;
Winkelmann 2007).
(b) Phytosiderophore: Iron is one metal, available in abundance in the soil,
an essential microelement for plant growth but even then, the plant faces the deficit
condition for this microelement. To escape such adverse conditions plant has secreted
specific chelating compounds “Phytosiderophore.” Phytosiderophores (PS) are the
organic substances (such as nicotinamine, mugineic acids (MAs), and avenic acid,
etc.) secreted by the roots of plants of graminae family (e.g., wheat, rice, maize,
sorghum, oat, barley, etc.) under Fe-deficient conditions (Mori and Nishizawa 1987).
The Phytosiderophore can form organic complexes or chelates with Fe
3+ and increase
the movement of iron in soil (Ueno et al. 2007). The iron (Fe)-phytosiderophore
complex enters the roots through an iron transporter channel present in the root
plasma membrane and endorsed the efficiency of Fe mainly in the area having low
soil Fe availability. The phytosiderophores are hexadentate ligands that coordinate
Fe
+3 with their amino and carboxyl groups (Singh et al. 2011). According to Wallace
(1991) phytosiderophore are non-proteineous, low molecular weight acids released
by the plants under the iron and zinc deficiency stress. The phytosiderophore mobilizes nutrient elements (like Fe, Zn, Mn, and Cu) from the soils to plant in deficient condition (Takagi et al. 1984). Fe-chelates are highly soluble and stable over
a wide pH range. In comparison with the molecular mass of microbial siderophores
(ranged 200–2000 Da) phytosiderophores are ranged between 500 and 1000 Da
(Neilands 1981). Mugineic acid (MA) is the most common siderophore and the
firstly identified in plants (Takemoto et al. 1978). The stability constant of the MAFe
+3 complexes is very low as compared with the stability constant of ferrichrome,
ferrioxamine B, and enterobactin microbial siderophores (Raymond et al. 1984;
Schwarzenbach and Schwarzenbach 1963; Harris et al. 1979). Some important
phytosiderophore which has been isolated from the gramineous plants are distichonic acid from Hordeum vulgare (beer barley) (Nomoto et al. 1981) avenic acid
A from Avena sativa (oat).
A plant releases phytosiderophore at higher amounts about a few hours (± 3 h) to
the onset of the light period. Under continuous darkness or continuous light, the rate
of release of phytosiderophore is lower. Further release of siderophores varies along
the root and is most pronounced in the apical root zone compared to the other zones
of the root. Morphologically highest uptake rates were found in highly branched
root system; whereas the lowest uptake rates were found in the thicken root system
(Romheld and Marschner 1990). Nature released of phytosiderophores is studied
with the help of high-performance liquid chromatography (HPLC) (Mori et al. 1991).
According to Cakmak et al. (1994) amount and composition of phytosiderophores
are affected by plant age, type and properties of soil, root morphology, crop varieties,
nutritional status of the plant, temperature, light duration, daytime vs light intensity.
Releasing rate of phytosiderophores by plants differs between plant to plant species
and is positively correlated with the plant resistance capacity to Fe deficiency.
G. Garg et al.
five groups, depending on their side chain group hydroxamate (Renshaw et al. 2002;
Winkelmann 2007).
(b) Phytosiderophore: Iron is one metal, available in abundance in the soil,
an essential microelement for plant growth but even then, the plant faces the deficit
condition for this microelement. To escape such adverse conditions plant has secreted
specific chelating compounds “Phytosiderophore.” Phytosiderophores (PS) are the
organic substances (such as nicotinamine, mugineic acids (MAs), and avenic acid,
etc.) secreted by the roots of plants of graminae family (e.g., wheat, rice, maize,
sorghum, oat, barley, etc.) under Fe-deficient conditions (Mori and Nishizawa 1987).
The Phytosiderophore can form organic complexes or chelates with Fe
3+ and increase
the movement of iron in soil (Ueno et al. 2007). The iron (Fe)-phytosiderophore
complex enters the roots through an iron transporter channel present in the root
plasma membrane and endorsed the efficiency of Fe mainly in the area having low
soil Fe availability. The phytosiderophores are hexadentate ligands that coordinate
Fe
+3 with their amino and carboxyl groups (Singh et al. 2011). According to Wallace
(1991) phytosiderophore are non-proteineous, low molecular weight acids released
by the plants under the iron and zinc deficiency stress. The phytosiderophore mobilizes nutrient elements (like Fe, Zn, Mn, and Cu) from the soils to plant in deficient condition (Takagi et al. 1984). Fe-chelates are highly soluble and stable over
a wide pH range. In comparison with the molecular mass of microbial siderophores
(ranged 200–2000 Da) phytosiderophores are ranged between 500 and 1000 Da
(Neilands 1981). Mugineic acid (MA) is the most common siderophore and the
firstly identified in plants (Takemoto et al. 1978). The stability constant of the MAFe
+3 complexes is very low as compared with the stability constant of ferrichrome,
ferrioxamine B, and enterobactin microbial siderophores (Raymond et al. 1984;
Schwarzenbach and Schwarzenbach 1963; Harris et al. 1979). Some important
phytosiderophore which has been isolated from the gramineous plants are distichonic acid from Hordeum vulgare (beer barley) (Nomoto et al. 1981) avenic acid
A from Avena sativa (oat).
A plant releases phytosiderophore at higher amounts about a few hours (± 3 h) to
the onset of the light period. Under continuous darkness or continuous light, the rate
of release of phytosiderophore is lower. Further release of siderophores varies along
the root and is most pronounced in the apical root zone compared to the other zones
of the root. Morphologically highest uptake rates were found in highly branched
root system; whereas the lowest uptake rates were found in the thicken root system
(Romheld and Marschner 1990). Nature released of phytosiderophores is studied
with the help of high-performance liquid chromatography (HPLC) (Mori et al. 1991).
According to Cakmak et al. (1994) amount and composition of phytosiderophores
are affected by plant age, type and properties of soil, root morphology, crop varieties,
nutritional status of the plant, temperature, light duration, daytime vs light intensity.
Releasing rate of phytosiderophores by plants differs between plant to plant species
and is positively correlated with the plant resistance capacity to Fe deficiency.