PLANT MINERAL NUTRITION
I. Criteria of essentiality (DI Arnon &
PR Stout, 1939)
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A. The element must be essential for normal
growth or reproduction, which can not proceed without it.
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B. The element cannot be replaced by another
element.
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C. The requirement must be direct, that is
not the result of some indirect effect such as relieving toxicity caused
by some other substance.
II. Essential elements for normal plant growth:
C HOPKNS CaFe Mg Na Cl .
(Mighty good) (Not always) (Clean)
CuMn CoZn MoB(y)!
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C = Carbon = Major structural component of
organic molecules
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H = Hydrogen = Major structural component
of organic molecules
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O = Oxygen = Major structural component of
organic molecules, final electron acceptor in Oxidative Phosphorylation
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P = Phosphorus = Important structural component
of nucleic acids, phospholipids, coenzymes
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K = Potassium = Important cofactor of some
enzymes, stomatal opening, membrane potentials, osmotic balance
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N = Nitrogen = Important structural component
of nucleic acids, proteins, chlorophyll, some phytohormones
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S = Sulfer = Important structural component
of some amino acids, forms disulfide bridges that are important to enzyme
activity
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Ca = Calcium = Important structural component
of middle lamella, cofactor for some enzymes, involved in membrane transport
phenomenon, forms crystals of toxic waste products
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Fe = Iron = Site of catalytic reaction in
may redox enzymes, essential for formation of chlorophyll
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Mg = Magnesium = Involved in stabilization
of ribosome particles, cofactor for many enxymes, structural component
of chlorophyll
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Na = Sodium = Benificial to Halophytes (Mangrove,
Atriplex, etc)
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Cl = Chlorine = Involved in photolysis of
water in photosynthesis
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Cu = Copper = site of catalytic reaction for
some enzymes
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Mn = Manganese = Resiratory enzyme cofactor,
involved in photolysis of water, required for auxin synthesis
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Co = Cobalt = Structural component of vitamin
B12, necessary for nitrogen fixation
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Zn = Zinc = Involved in auxin synthesis, enzyme
cofactor
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Mo = Molybdenum = Involved in reduction of
nitrates
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B = Boron = Involved in translocation and
absorption of sugar, interacts with Ca flux
III. Commercial Fertilizers sold as
%N, %P, %K
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eg. 20-10-5 = 20%N, 10%P, 5%K
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Good Soils = 25% Air, 25% Water, 2% Organics,
48% Mineral
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Mineral particles (-) bind elements with +
charges (Ca++) but not elements with - charges (PO - 4)
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Recent estimates indicate 70% of all Nitrogen
within Nitrogen cycle on Earth is currently contributed by human activity