Post on 03-Apr-2018
7/28/2019 The Importance of Macronutrients and Micronutrients in Plants
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Green plants are autotrophic organism that
functions as producers in ecosystems.
They are able to synthesise their ownnutrients by means of photosynthesis.
To carry out photosynthesis, they require raw
materials in the forms of inorganicsubstance, that is, carbon dioxide, water and
mineral nutrients.
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The elements required by plants can be
classified into macronutrients and
micronutrients based on the amount needed.
Macronutrients are elements required by
plants in large quantities
Micronutrients or trace elements areelements required by plants in traces or
small quantities.
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Macronutrients and micronutrients are
required to synthesise substances essential
for the healthy growth of plants.
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Macronutrients are :
Carbon (C)
Hydrogen (H)
Oxygen (O)
Nitrogen (N)
Phosphorus (P)
Potassium (K)
Calcium (Ca) Magnesium (Mg)
Sulphur (S)
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Carbon dioxide and water are sources of the
three important macronutrients, namely
carbon, hydrogen, and oxygen.
Other macronutrients required by plants are
obtained from the soil in the form of
inorganic ions.
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Carbon, hydrogen and oxygen are major
elements required by plants for the synthesis
of organic substance such as carbohydrates,
proteins, and lipids.
Besides the macronutrients, plants also
require other minerals even though in small
quantities.
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Micronutrients are
Boron (B)
Molybdenum (Mo)
Zinc (Zn) Manganese (Mn)
Copper (Cu)
Iron (Fe)
Chlorine (Cl)
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Micronutrients are required to activate some
enzymes involved in cellular metabolism such
as respiration. They may act as cofactors or
form part of coenzymes.
The absence of mineral nutrients will lead to
mineral deficiencies in plants.
Investigations on the effects of nutrient
deficiencies in plants can be done using
culture solution.
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A plant which grows in such a solution is then
compared to another plant which grows in a
complete Knops solution.
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Knops solution is a complete culture solution
and its contents are as follows
Calcium nitrate 0.8gPotassium nitrate 0.2g
Potassium dihydrogen phosphate 0.2g
Magnesium sulphate 0.2g
Iron (III) phosphate 0.2g
Distilled water 1 litre
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We can investigate whether a plant requires
a particular mineral element and the effect
of its deficiency by eliminating if rom Knops
solution.
For example, to study the effects of the
deficiency of magnesium, the magnesium
sulphate (MgSO4) in Knops solution isreplaced with potassium sulphate (K2SO4).
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Macronutrient Function Effects of deficiencies
Nitrogen (N) as a major component of
amino acids, nucleic acids
chlorophyll, enzymes and
coenzymes
promotes stem and leaf
growth
Chlorosis of leaves in
which synthesis of the
green pigment,
chlorophyll, is inhibited
resulting in a pale yellow
colouration
Stunted growth
Reduced yields
Phosphorus (P) As a component of nucleic
acids, adenosinetriphosphate (ATP) and
phospholipids in plasma
membrane
Needed for
photosynthesis and seed
germination
Poor root growth and
stunted growth of plant Formation of dark green
leaves with red or purple
spots on old ones
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Macronutrient Function Effects of deficiencies
Potassium (K) As a cofactor for
many enzymes
involved in protein
synthesis and
carbohydrate
metabolism
Involved in water
balance andregulates the
opening of stomata
Stunted growth
Yellowing of leaves
followed by dying of
leaf tips and edges
Premature death of
plants
Calcium (Ca) Needed for cell wall
formation
Regulates
movements of
substances across
cell membrane
Stunted growth
Causes leaves to
become irregular,
distorted and
cupped
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Macronutrient Function Effects of deficiencies
Magnesium (Mg) As a component
of chlorophyll
Activates many
plant enzymes in
carbohydrate
metabolism
Yellowing of
leaves, sometimes
with red spots on
leaf surfaces
Sulphur (S) As a component
of certain amino
acids and certain
coenzymes
involved in
respiration
Initial yellowing of
young leaves
spreading to
whole plant
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Macronutrient Function Effects of deficiencies
Boron (B) Helps in translocation
of sugars, calcium
uptake and
germination of pollen
grains
Involved in
carbohydrate
metabolism and
needed for cell division Acts as a cofactor in
chlorophyll synthesis
Leaves become thick,
curled and brittle
Death of terminal buds
Abnormal growth
Molybdenum (Mo) Involved in nitrogen
fixation during protein
synthesis
Pale green leaves
Chlorosis between
veins of mature leaves
Reduces crop yield
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Macronutrient Function Effects of deficiencies
Zinc (Zn) As a cofactor in
carbohydrate
metabolism Needed for the
synthesis of auxin
Formation of leaves
Stunted growth
Leaves with irregular
areas of chlorosis
Reduced leaf size
Manganese (Mn) Activates the
enzymes involved in
photosynthesis,
respiration and
nitrogen
metabolism
Pale green leaves
with a network of
green veins
Grey spots appear
between veins
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Macronutrient Function Effects of deficiencies
Copper (Cu) As component of
enzymes
Involved in
photosynthesis, as wellas carbohydrate and
nitrogen metabolism
Needed for flower
formation and
reproductive growth
Required for lignin
synthesis which is
needed for cell wall
strength and
prevention of wilting
Stunted growth
Yellowing of leaves
Brown spots appear in
terminal leaves Wilting and eventual
death of tips of young
shoots
Iron (Fe) As a cofactor in the
synthesis of
chlorophyll
Required for the
growing parts of
plants
Stunted growth
Chlorosis in
between veins of
young leaves
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