obtained from the soil. Soil essential elements have been classified on the basis of
(Evans and Sorger 1966, Mengel and Kirkby 1987; Table 5.1; Fig 5.1) the following:
1. Mobility in plants: mobile elements (N, P, K, Cl, Mg, Mo) and immobile elements
(Ca, Cu, Fe, Mn, Ni, S, Zn)
2. Requirements: macro-nutrients (N, P, K, S, Ca, Mg, Si) and micro-nutrients (Cl,
Fe, B, Mn, Na, Zn, Cu, Ni, Mo)
3. Functions:
(a) group1: part of carbon compounds (N, S)
(b) group 2: in energy storage (P, Si, B)
Table 5.1 Essential elements from soil classified into macro- and micro-elements, forms taken up
by plants, and function
Macroelements
Form available
for plants
Function
Nitrogen (N)
NO
3À and NH
4
+
nucleic acids (RNA, DNA), amino acids, hormones
Phosphorus
(P)
PO
3À
DNA, RNA, proteins, lipids, sugars, ATP, ADP, and
NADPH
Potasium (K)
K
+
cofactor for many enzymes, maintain cell electronutrility
and turgour
Sulfur (S)
SO 4
2À
amino acids (cysteine, methionine), coenzymes, vitamins,
several secondary metabolites
Calcium (Ca)
Ca
2+
Secondary messanger, part of cell wall, cofactor for several
enzymes
Magnesium
(Mg)
Mg
2+
Part of chlorophyll molecule and important enzymes
Silicon (Si)
Silicic acid
Contributes to the mechanical strength of cell wall
Micronutrients
Iron (Fe)
Fe
2+ and Fe
3+
enzyme cofactors , components of electron transport chains (
FeS and haem)
Chlorine (Cl)
Cl
À
Stomatal Regulation, Photosynthetic O 2 evolution,
Osmoregulation
Boron (Bo)
H 3 B 3
plant cell wall,Cell division ,movement of sugar,pollination
and seed set,nitrogen and carbohydrate metabolism
Molybdenum
(Mo)
MoO 4
2À
Cofactor in various enzymes ,nitrogenase and nitrate
reductase enzyme
Manganese
(Mn)
Mn
2+
carbohydrate metabolism,electron transport in
photosynthesis,cofactor of various enzymes
Copper (Cu)
Cu
+ , Cu
2+
plastocyanin,cofactor of a large number of oxidases
Zinc (Zn)
Zn
2+, Zinc
complexes
maintaining the activity of DNA polymerase enzymes, act as
cofactors in metalloenzymes and required at active sites of
various enzymes
Nickel (Ni)
Ni
+
Constituent of Urease and hydrogenase
Sodium (Na)
Na
+
plays role in regenertaion of phosphoenolpyruvate in C4 and
CAM plants
5 Plant Roots and Mineral Nutrition: An Overview of Molecular Basis of Uptake and. . . 133
(Evans and Sorger 1966, Mengel and Kirkby 1987; Table 5.1; Fig 5.1) the following:
1. Mobility in plants: mobile elements (N, P, K, Cl, Mg, Mo) and immobile elements
(Ca, Cu, Fe, Mn, Ni, S, Zn)
2. Requirements: macro-nutrients (N, P, K, S, Ca, Mg, Si) and micro-nutrients (Cl,
Fe, B, Mn, Na, Zn, Cu, Ni, Mo)
3. Functions:
(a) group1: part of carbon compounds (N, S)
(b) group 2: in energy storage (P, Si, B)
Table 5.1 Essential elements from soil classified into macro- and micro-elements, forms taken up
by plants, and function
Macroelements
Form available
for plants
Function
Nitrogen (N)
NO
3À and NH
4
+
nucleic acids (RNA, DNA), amino acids, hormones
Phosphorus
(P)
PO
3À
DNA, RNA, proteins, lipids, sugars, ATP, ADP, and
NADPH
Potasium (K)
K
+
cofactor for many enzymes, maintain cell electronutrility
and turgour
Sulfur (S)
SO 4
2À
amino acids (cysteine, methionine), coenzymes, vitamins,
several secondary metabolites
Calcium (Ca)
Ca
2+
Secondary messanger, part of cell wall, cofactor for several
enzymes
Magnesium
(Mg)
Mg
2+
Part of chlorophyll molecule and important enzymes
Silicon (Si)
Silicic acid
Contributes to the mechanical strength of cell wall
Micronutrients
Iron (Fe)
Fe
2+ and Fe
3+
enzyme cofactors , components of electron transport chains (
FeS and haem)
Chlorine (Cl)
Cl
À
Stomatal Regulation, Photosynthetic O 2 evolution,
Osmoregulation
Boron (Bo)
H 3 B 3
plant cell wall,Cell division ,movement of sugar,pollination
and seed set,nitrogen and carbohydrate metabolism
Molybdenum
(Mo)
MoO 4
2À
Cofactor in various enzymes ,nitrogenase and nitrate
reductase enzyme
Manganese
(Mn)
Mn
2+
carbohydrate metabolism,electron transport in
photosynthesis,cofactor of various enzymes
Copper (Cu)
Cu
+ , Cu
2+
plastocyanin,cofactor of a large number of oxidases
Zinc (Zn)
Zn
2+, Zinc
complexes
maintaining the activity of DNA polymerase enzymes, act as
cofactors in metalloenzymes and required at active sites of
various enzymes
Nickel (Ni)
Ni
+
Constituent of Urease and hydrogenase
Sodium (Na)
Na
+
plays role in regenertaion of phosphoenolpyruvate in C4 and
CAM plants
5 Plant Roots and Mineral Nutrition: An Overview of Molecular Basis of Uptake and. . . 133