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SUBTOPICS
Mineral nutrition important
Classification of minerals
Roles and properties 0f minerals
Deficiency symptoms 0f minerals
Why Is Mineral Nutrition Important?
In most natural soils, the availability of mineral nutrients limits plant growth and primary productivity.
Nutrient limitation is an important selective pressure and plants face many special changes related to the need to acquire and use mineral nutrients efficiently.
“Plant nutrition” specifically does not refer to photosynthesis.
Classification Of Minerals:
On the basis of the amounts found in plants:
Macronutrients: N, K, Ca, Mg, P, S, Na, (Si)
Micronutrients: Cl, Fe, B, Mn, Zn, Cu, Mo, Ni
Essential Elements :
What defines an “essential” element?
1. In its absence the plant cannot complete a normal life cycle
2. The element is part of an essential molecule
(macromolecule, metabolite) inside the plant
Most elements fall into both categories above (e.g., structural
vs. enzyme cofactor)
These 17 elements are classified as
9 macronutrients (present at > 10 mmol / kg dry wt.)
8 micronutrients (< 10 mmol / kg dry wt.)
Hydroponic culture can determine which mineral elements
are actually essential nutrients.
Essential Elements :
Classification of minerals:
Macronutrients are elements required by plants
in relatively large quantities (9 total).
Organic compounds: Carbon, oxygen, hydrogen,
nitrogen, sulfur, and phosphorus.
The other three are potassium, calcium, and
magnesium.
Micronutrients elements are nutrients that the
plants need in very small amounts (8 total).
Iron, chlorine, copper, zinc, manganese,
molybdenum, boron, and nickel.
Most function as cofactors of enzymatic reactions.
Classification of minerals:
Name Chemical Relative Function in plant
symbol % in plant
to N Primary macronutrients
Nitrogen N 100 Proteins, amino acids
Phosphorus P 6 Nucleic acids, ATP
Potassium K 25 Catalyst, ion transport
Secondary macronutrients
Calcium Ca 12.5 Cell wall component
Magnesium Mg 8 Part of chlorophyll
Sulfur S 3 Amino acids
Iron Fe 0.2 Chlorophyll synthesis
Micronutrients
Copper Cu 0.01 Component of enzymes
Manganese Mn 0.1 Activates enzymes
Zinc Zn 0.03 Activates enzymes
Boron B 0.2 Cell wall component
Molybdenum Mo 0.0001 Involved in N fixation
Chlorine Cl 0.3 Photosynthesis reactions
ROLES, PROPERTIES AND DEFICIENCY
SYMPTOMS OF MINERALS
CARBON (C):
Roles and properties:
Basic structural element of life.
Although not very plentiful in the earth's crust (<0.1%),
carbon is one of the most abundant elements in living
things.
It occurs in plants combined with hydrogen and oxygen in
the form of hydrocarbons., and in their geological
derivatives, petroleum and coal.
Carbon also occurs in the atmosphere as CO2, and in
rocks as carbonate minerals such as limestone.
Deficiency symptoms:
Very serious, no growth!
OXYGEN (O):
Roles and properties:
Powerful oxidizing agent .
Oxygen is the most abundant element in the earths crust
on the basis of both mass and number of atoms (49.5%
of the mass of the earths crust is oxygen atoms).
In the free state oxygen occurs in the atmosphere as O2
molecules (21% of air by mass).
In the combined state, oxygen occurs in many minerals,
living things and water.
Deficiency symptoms:
No Respiration.
HYDROGEN (H):
Roles and properties:
Lightest element, and a powerful reducing agent.
Most abundant element in the universe.
In the earth's crust hydrogen is third in abundance on an atom
basis. On a mass basis, it is ninth in order of abundance .
Free, uncombined hydrogen is very rare.
However, combined hydrogen is quite common (eg., water, and
organic compounds).
Supplied in the mobile oxidized form of H2O, and made available
as a reducing element by photosynthesis.
Forms covalent bonds with the electronegative elements C, N, O
and H. Pretty important for hydrogen bonding!
Deficiency symptoms: Can't Happen.
NITROGEN (N):
Roles and properties:
About 1/3 as abundant as carbon. Occurs principally as
diatomic N2 in the atmosphere.
Makes + charged groups possible.
Amine N is important in complexing metals (eg., binding Fe in
cytochromes, or binding Mg in chlorophyll).
Acts as a donor atom in many enzymatically catalyzed
reactions.
In living things, N is found almost exclusively in the fully
reduced state.
Most of the N absorbed from the soil by higher plants is in the
fully oxidized form of NO3, and must be reduced for assimilation.
NITROGEN (N):
Deficiency symptoms:
General chlorosis, especially of older leaves
(mobile).
In severe cases these leaves yellow and die.
Younger leaves remain green longer,
because they receive soluble forms of
nitrogen transported from older leaves.
In many plants, excess nitrogen often
stimulates shoot growth more than root
growth and may favor vegetative growth over
flowering and seed formation.
PHOSPHOROUS (P):
Roles and properties:
Occurs and reacts as orthophosphate, the fully oxidized and
stable form.
Participates in metabolism by forming water-stable phosphate
esters and anhydrides. In these forms P has several
fundamental roles:
Linkage (as in nucleic acids),
Source of free energy in bond formation (Carries chemical
energy in ATP).
Component of sugar-phosphates; (in DNA & RNA)
Component of phopholipids (in membranes)
Mg++ (or Mn++) is a required cofactor in reactions involving
phosphate transfer. Mg++ also commonly neutralizes
polyphosphate compounds.
PHOSPHOROUS (P):
Deficiency symptoms:
Phosphorous-deficient plants are stunted (stop growth) and , in contrast to those lacking nitrogen, are often dark green.
Phosphate is easily redistributed (mobile) in most plants from one organ to another and is lost from older leaves, accumulating in younger leaves, developing flowers and seeds. As a result, deficiency symptoms occur first in more mature leaves.
SULFUR (S):
Roles and properties:
Occurs primarily in reduced form in living things.
Disulfides are more stable than dioxides (or peroxides),
permitting -SH participation in redox reactions (-SH + HS- ---- -S-
S-).
SH groups are also form hydrogen bonds.
SH groups can be the reactive sites of enzymes or coenzymes
(Coenzyme A) and are important for protein conformation.
Sulfate (SO4=) from the soil is the primary source of S, although
some SO2 is absorbed from the atmosphere (too much SO2
can be quite toxic to plants.
Sulfate reduction is very energy intensive and occurs mainly in
chloroplasts (we will see this later along with photosynthesis).
SULFUR (S):
Deficiency symptoms:
General chlorosis of leaf, including
vascular bundles.
Sulfur is not easily redistributed
(immobile) from mature tissues in
some species, so deficiencies are
usually noted first in younger leaves.
POTASSIUM (K+):
Roles and properties:
Dominant cation in plants.
K+ is an activator of many enzymes that are essential for
photosynthesis and respiration, and it also activates
enzymes needed to form starch and proteins.
K+ is quite mobile in the plant, because there are many
membrane carrier systems adapted to K+.
It is a major contributor to the osmotic potential of cells and
therefore to their turgor pressure.
K+ regulation of osmotic potentials forms the basis for
turgor movements in plants (eg., stomate opening, leaf
movements).
POTASSIUM (K+):
Deficiency symptoms:
As with N and P, K+ is easily
redistributed (mobile) from mature
to younger organs, so symptoms
first appear in older leaves.
Leaves develop necrotic lesions
and light chlorosis.
The tips often die first.
K+ deficient cereals develop weak
stems so they are easily fall.
CALCIUM (CA++):
Roles and properties:
Often the most abundant divalent cation in plants.
Important component of cell walls.
It stabilizes the polysaccharides by forming intermolecular
complexes with -COO- groups of pectins.
Calcium is also important for maintaining the safety of
membranes, especially the plasma membrane.
Free calcium concentration in the cytosol is normally very low,
about 10-7 M. Some hormonal or environmental signals raise
the free Ca++ concentration to 10-6 to 10-5 M.
Because changes in calcium are associated with hormonal and
environmental signals it is often referred to as a secondary
messenger.
CALCIUM (CA++):
Deficiency symptoms:
Meristematic regions die.
Margins of younger leaves
become chlorotic then necrotic.
Young leaves are distorted.
Symptoms appear first in young
tissues since Ca++ is not very
mobile.
MAGNESIUM (MG++):
Roles and properties:
Most important divalent cation in enzymatic catalysis.
Involved in most reactions involving ADP and ATP.
Activates enzymes for DNA and RNA synthesis.
Constituent of chlorophyll.
Activates key enzymes involved in CO2 fixation.
Has structural roles in membranes, especially in organelles.
MAGNESIUM (MG++):
Deficiency symptoms:
Deficiency causes extensive
interveinal chlorosis which
starts with basal leaves (older)
and progresses to younger
leaves (mobile).
IRON (Fe++):
Roles and properties:
Important for its oxidation-reduction properties (Fe+++ to
Fe++).
Iron forms a locus for electron transfer in many enzymes
(eg., cytochromes, peroxidases, catalyses).
It is also required for chlorophyll synthesis.
Iron is a difficult cation for plants to handle since it readily
precipitates.
IRON (FE++):
Deficiency symptoms:
Extensive interveinal chlorosis, starting with younger leaves
(iron is relatively immobile).
Similar to Mg deficiency except in younger leaves.
COPPER (CU++):
Roles and properties:
Important for its oxidation-reduction properties (Cu++
to Cu+)
Copper is an important component of several critical
enzymes (eg., plastocyanin for photosynthesis and
cytochrome oxidase for respiration).
COPPER (CU++):
Deficiency symptoms:
Plants need very little copper so they are rarely deficient in it
(usually sufficiently available in soil).
Experimentally, copper deficiency leads to distorted and dark
green younger leaves. (immobile)
MOLYBDENUM (MO6+):
Roles and properties:
Important for its oxidation-reduction properties.
It is a key component of nitrate reductase where it
functions as an e- carrier for nitrate reduction.
It is also important in organisms that can carry out
nitrogen fixation (from N2).
MOLYBDENUM (MO6+):
Deficiency symptoms:
Most plants require less
molybdenum than any other
element, so deficiencies are rare.
Symptoms often consist of
interveinal chlorosis, first in older
leaves. (mobile)
Young leaves may be severely
twisted (whiptail disease).
MANGANESE (MN++):
Roles and properties:
Important for its oxidation-reduction properties.
A major role for manganese is in the removal of
electrons from water during photosynthesis (water
oxidation).
Manganese also is essential in respiration and
nitrogen metabolism.
It can function effectively in some metal catalyzed
enzymatic reactions which require magnesium.
MANGANESE (MN++):
Deficiency symptoms:
However, deficiencies are rare since
low amounts are required and it is
usually in plentiful supply in soil.
The absence of Manganese causes
disorganization of chloroplast
thylakoid membranes.
Plants become chlorotic.
ZINC (ZN++):
Roles and properties:
Important in enzymes with
oxidation-reduction properties.
Deficiency symptoms:
Interveinal chlorosis and
inhibition of stem growth.
Leaf margins are distorted and
puckered.
BORON (B(OH)3):
Roles and properties:
Specific function unknown. However, boron is
found in cell walls complexed with raffinose-
containing polymers.
It is also found in phloem complexed with
sorbitol.
pollen tubes can't elongate without boron.
Some research suggests a role for boron
during synthesis of nucleic acids.
Deficiency symptoms:
Several disorders related to disintegration of
internal tissues such as "heart rot" of beets and
"stem crack" of celery .
Root and shoot tips stop growing.
CHLORIDE (CL-):
Roles and properties:
Plants frequently contain a good deal of chloride but very little is required as a nutrient.
It has important functions in photosynthesis.
It may play a general role in maintaining electrical equilibrium.
Deficiency symptoms:
The leaves have abnormal shapes, with distinct interveinal chlorosis.
ROLES AND PROPERTIES:
Sodium (Na+):
Essential for some halophytes.
Sodium can replace potassium where it is deficient.
Exact functions unknown. May be important for maintaining
electrical equilibrium.
Silicon (Si4+):
Abundant in soils. Absorbed from soils as silicic acid (H4SiO4).
Is used by some plants to strengthen cell walls (eg., rice, oats,
equisetum).
Cobalt:
Not required by plants, but required by the bacteroids of root
nodules which fix N2, and thus indirectly in nitrogen nutrition.
Element Function
C,H,O Throughout the plant, organic compounds, sugars,
cellulose, starch, lipids, . . .
N Component of amino acids (required for protein
synthesis), nucleic acids (DNA, RNA), chlorophyll
K Regulates osmotic balance, especially in stomatal
Opening/closing; enzyme activator
Ca Major component of the cell wall; enzyme cofactor;
component of calmodulin (signal transduction
component); mediates membrane permeability
P Carries chemical energy in ATP, sugar-phosphates;
component of DNA & RNA; component of
phopholipids (in membranes)
A summary of the functions of inorganic
nutrients in plants.
Element Function
Mg Cofactor of chlorophyll; enzyme activator
S Component of 2 amino acids (forms disulfide bonds
in proteins); cofactor of enzymes (coa)
Fe Cofactor of cytochromes (electron transfer proteins);
required for chlorophyll synthesis
Cl Regulates osmotic balance; component of
photosynthetic reaction center (PSII)
Cu Cofactor of photosynthetic electron transfer protein
(Plastocyanin), respriratory electron transfer protein
(Cytochrome c oxidase) and of other enzymes
A summary of the functions of inorganic nutrients in
plants.
Element Function
Mn Component of photosynthetic reaction center (PSII);
cofactor of some enzymes
Zn Enzyme cofactor
Mo Required for nitrogen fixation and nitrate (NO3
-) Reduction
B Mediates ca utilization, nucleic acid synthesis, and
lignin synthesis
Ni Constituent of the enzyme urease
Na Regulates osmotic balance in some plants; required
for C4 photosynthesis
Si Cell wall structural element in rice & equisetum
A summary of the functions of inorganic nutrients in
plants.
Element Deficiency symptoms
Symptoms in older leaves first
N Stunted growth; pale green, yellow, or brown leaves;
slender stems; anthocyanin accumulation
K Mottled or chlorotic leaves (faded green/yellow)
with dead spots (necrosis); curling or crinkling
P Stunted growth, dark green leaves with dead spots
(necrosis); some anthocyanin accumulation
Mg Mottled or chlorotic leaves (interveinal); tips &
edges of leaves curl upward
Common mineral deficiency symptoms observed in
plants.
Element Deficiency symptoms
Symptoms in younger leaves first
Ca Young leaves at bud hooked, then die back at
edges, stalk dies at bud
B Young leaves of the terminal bud light green,
leaves twisted, stalk dies at bud
S Chlorosis, young leaves light green; some
anthocyanin accumulation
Fe Young leaves chlorotic (interveinal)
Cu Young leaves wilted, wilted terminal bud, dark
green leavesw/necrosis
Common mineral deficiency symptoms observed in
plants.
Element Deficiency symptoms
Symptoms in younger leaves first
Mn Chlorosis (interveinal), necrosis
Zn Rosette growth, leaves small, puckered (makes
less auxin)
Mo Interveinal chlorosis, necrosis; poor flowering;
can cause N deficiency
Cl Wilting at leaf tips; general chlorosis & necrosis,
bronzing, stunted
Common mineral deficiency symptoms observed in
plants.
