Agriculture Reference
In-Depth Information
Table 4.1 (continued)
Mineral nutrient and its
availability
Physiological role
Deficiency symptoms
Sodium: present as Na
+
ion
Stimulates growth by affect-
ing cell expansion and water
balance of plants, replaces
potassium (K
+
) as solute, par-
ticipates in C
4
and CAM
pathways
Chlorosis, necrosis
Silicon: present as SiO
2
in soil Deposited in the form of
hydrated amorphous silica
(SiO
2
Increases the susceptibility to
lodging (falling over) and
fungal infection
n
H
2
O) mainly in endo-
plasmic reticulum, cell wall,
intercellular spaces
Chlorine: present as chlorine
ion (Cl
)
Required in photosynthesis,
cell division
Rare, causes wilting of leaves
and subsequent chlorosis and
necrosis
Iron: present as Fe
2+
(ferrous)
and Fe
3+
(ferric) ions
Involved in redox reactions,
required for the synthesis of
chloroplast-protein complexes
in chloroplast
Intervenous chlorosis, whit-
ening of leaves
Boron: present as boric acid
(H
3
BO
3
) and borate (H
2
BO
3
)
Role in cell cycle regulation,
nucleic acid synthesis, cell
elongation, membrane
function
Black necrosis of young
leaves, loss of apical domi-
nance (leading to increased
branching)
Manganese: present as Mn
2+
ions
Mn
2+
activates many enzymes
involved in Krebs cycle,
involved in photosynthetic
reactions
Intervenous chlorosis along
with necrotic spots
Zinc: present as Zn
2+
ions
Integral component of many
enzymes (alcohol dehydroge-
nase, carbonic anhydrase,
alkaline phosphatase, etc.),
structural component of ribo-
somes, maintains integrity of
biomembranes
Rosetting (stunted growth
due to shortening of inter-
nodes), small leaves, severe
deficiency causes death of
shoot apices
Copper: present as Cu
2+
Bound with enzymes of redox
reactions (plastocyanin)
Dark green leaves, necrotic
spots arising from tip and
extending toward margin
Molybdenum: present as
MoO
4
ions
Component of enzymes
(nitrate reductase and nitroge-
nase) involved in nitrate
assimilation and nitrogen fix-
ation, thus causing nitrogen
deficiency
Chlorosis, necrosis, prema-
ture flower abscission
Nickel: present predominantly
as Ni
2+
Component of urease
Accumulation of urea in
leaves and subsequent
necrosis
