Transcript Chlorosis

Plant Mineral Nutrition
Mineral Nutrition
• The study of how plants obtain and use
mineral nutrients is called plant mineral
nutrition.
Importance of mineral nutrition
• Green plants are autotrophic i.e. can synthesize their
organic food from inorganic source
• Animals are heterotrophic i.e. can not synthesize their
organic food from inorganic source and depend directly
or indirectly on plants for their food.
• All plants require basic constituents/components for
synthesis of food and functioning of metabolism.
• Plants essentially require inorganic nutrients e.g. carbon,
hydrogen, oxygen, nitrogen, phosphorus, potassium,
sulphur, iron, manganese etc.
Essential and beneficial elements
• Scientists have determined the whole
profile of elements in plants
• More than 60 elements are required for
plant growth but all are not essentially
required
• Out of 60, 22 elements are essentially
required
Essential elements
• i) An element without which a plant cannot
complete its life cycle; ii) Must not be
replaceable by another element; iii) Must be
directly involved in plant metabolism (Arnon and
Stout, 1939).
• An element which has a clear physiological role
(Epstein, 1999).
• If an element is deficient in a plant, specific
deficiency symptoms will occur in plant.
Beneficial elements
• Those elements when they are present, they
stimulate the growth of plants but they are not
essentially required for plant growth.
• Plant growth will be better in the presence of
beneficial elements.
• Beneficial elements are 5 in number i.e. Na, Ni,
Si, Se, and Co (In some plants some of these
elements act as essential elements)
Beneficial elements as essential
elements
• Sodium: there are 3 indicators of Na i) Kochia
indica ii) Suaeda iii) Salsola
• Nickel:Ni is essential in some plants e.g. in Jack
bean (this plant cannot complete life cycle
without Ni)
• Silicon: Si is essential in some monocots e.g.
grasses. In these plants Si is deposited around
cell wall so they are more resistant to
environmental stresses than the dicots. In rice
16.4% is deposited in its cell wall.
Continuo--• Selenium: It is essentially required for
Astragalus, widely grown in California and
is known as indicator of Se.
• Cobalt: It is essential in Cyanobectria and
Rhizobia.
• Antagonistic
effects:
When
level
or
concentration of one element increases, it will
lower down the concentration of other nutrient or
effect of other nutrient e.g. phosphorus uptake is
antagonistic by Ca2+.
• Nutrient efficient varieties: varieties which
show better performance by absorbing low
concentration of nutrients or good performance
even in nutrient deficient soils.
Nutritional deficiency
Nutritional deficiency may due to one of the
following reasons:
1. Non availability of particular element in soil
2. One nutrient is present in sufficient amount
and cause the deficiency of other element
“nutrient specific effect”
3. Due to certain viral induced diseases. These
symptoms may b closely related to those
caused by a particular nutrient deficiency
Study of nutrients’ deficiency
•
There are three well known methods to
study nutrients deficiency
1) Hydroponics: The technique of growing
plants with their roots emerged in
nutrient solution without soil is called
hydroponics or solution culture.
2) Nutrient film growth system: It is used to
save excess amount of nutrient solution
3) Aeroponic growth system:
Hydroponics or solution culture
Aeroponic growth system
Nutrient film growth system
Classification of mineral nutrients
• Based on concentration: nutrients are
classified in plant tissues on the basis of
how much nutrients are present in tissues
e.g. in roots concentration of particular
nutrient is high as compared to leaves.
• i) Major or Macro-nutrients
• ii) Minor or Micro-nutrients
Dry mass basis (Epstein, 1972, 1999)
Major
H
C
O
N
K
Ca
Mg
P
S
Si
ppm
60000
45000
45000
15000
10000
5000
2000
2000
1000
1000
Minor
Cl
Fe
B
Mn
Na
Zn
Cu
Ni
Mo
ppm
100
100
20
50
10
20
6
0.1
0.1
2. Source of availability
• There are different sources e.g. air, soil
• i) Atmosphere: Atmosphere contains C, H and
O in the form of CO2 and H2O
• ii) Soil: Soil nutrients can be categorized into
macro and micro nutrients.
• When nutrients are present in more than 1000
ppm conc., they are known as major
• Micronutrients are those which are required in
small amounts. If they are present in larger
quantity, they will be toxic for plants
3. On the basis of physiological
functions or biochemical reactions
• On the basis of physiological functions, there are 4
groups
• Group I: (N, S)
• These elements are part of carbon compounds. This
group has only two elements
• i) nitrogen
• ii) sulfur
• Nitrogen: It is constituent of amino acids, nucleic acids,
amides, proteins etc.
• Its uptake from the soil is in the form of nitrate and
ammonium (toxic for plants)
• Essential for plant cell division, vital for plant growth
• Directly involved in photosynthesis
• Necessary component of vitamins
• Aids in production and use of carbohydrates
• Sulfur: It is constituent of amino acids (cystein, methionine),
proteins etc. It is taken up by the plants in form of sulfate.
• Integral part of amino acids
• Helps develop enzymes and vitamins
• Promotes nodule formation on legumes
• Aids in seed production
• Necessary in chlorophyll formation (though it isn’t one of the
constituents)
• Group II: (P, Si, B)
• Nutrients included in this group are important in energy storage or
structural integrity. It contains 3 nutrients:
• i) Phosphorus
• ii) Silicon
• iii) Boron
• Phosphorus: main component of sugar phosphates, required for
conversion of ADP to ATP, uptake form is phosphate (key role in
ATP formation)
• Involved in photosynthesis, respiration, energy storage and transfer,
cell division, and enlargement
• Promotes early root formation and growth
• Improves quality of fruits, vegetables, and grains
• Increases water-use efficiency
• Silicon: It is deposited as amorphous silica in
cell wall, uptake form is monosilicic acid or
monosilicate
• Boron: Boron is taken up by plants primarily as
H3BO3 (boric acid) and H2BO3- (borate)
• Essential for formation of pollen grains and
growth of pollen tubes
• Essential for seed and cell wall formation
• Promotes maturity
• Necessary for sugar translocation. Boron plays
an important role in the movement and
metabolism of sugars in the plant and synthesis
of plant hormones and nucleic acids.
Group III: (K, Ca, Mg, Cl, Mn, Na)
It contains 6 elements and all are absorbed in ionic form.
• Potassium: cofactor for more than 40 enzymes.
Carbohydrate metabolism and the break down and
translocation of starches
• Increases photosynthesis
• Increases water-use efficiency
• Essential to protein synthesis
• Important in fruit formation
• Improves quality of seeds and fruit
• Increases disease resistance
• Calcium: important role in membrane stability. Utilized
for Continuous cell division and formation
• Involved in nitrogen metabolism
• Reduces plant respiration
• Aids translocation of photosynthates from leaves to
fruiting organs
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Magnesium:
Key element of chlorophyll production
Improves utilization and mobility of phosphorus
Activator and component of many plant enzymes
Increases iron utilization in plants
Influences earliness and uniformity of maturity
Chloride:
Not much information about its functions
Interferes with P uptake
Enhances maturity of small grains on some soils
Manganese:
Functions as a part of certain enzyme systems
Aids in chlorophyll synthesis
Increases the availability of P and Ca
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Sodium: acts as an essential elements for few species
Group IV: (Fe, Cu, Zn, Ni, Mo)
This group involves elements involved in redox reactions
Iron: Promotes formation of chlorophyll
Acts as an oxygen carrier
Reactions involving cell division and growth, uptake is in
the form of ferrous (Fe2+)
Copper: Catalyzes several plant processes
Major function in photosynthesis
Major function in reproductive stages
Indirect role in chlorophyll production
Increases sugar content
whether it is absorbed as Cu or as chelate form.
Zinc: Aids plant growth hormones and enzyme system
Necessary for chlorophyll production
Necessary for carbohydrate formation
Necessary for starch formation
Aids in seed formation, uptake the form of zinc ion
• Ni: uptake is also not clear
• Mo: uptake form is molybdate (ammonium
molybdate, sodium molybdate)
• Required to form the enzyme "nitrate reductase"
which reduces nitrates to ammonium in plant
• Aids in the formation of legume nodules
• Needed to convert inorganic phosphates to
organic forms in the plant
Classification on the basis of
mobility
• Nutrients can be divided into two groups on the
basis of mobility
• Mobile nutrients: Those nutrients which can be
translocated from one part to the other through
phloem e.g. N, K, Mg, Mn, Cl, P, Na, Zn, Mo
• Immobile nutrients: Those nutrients which can
not be translocated from one part to the other
through phloem. They can be transported
through xylem e.g. Ca, S, Fe, B, Cu, Si
Deficiency symptoms
• Reduction in growth:
• Reduction in growth takes place due to specific
reasons
• Parts of plants that show symptoms:
• Younger or older leaves
• Stem
• Roots
• In case of deficiency of mobile nutrients
symptoms will appear on older leaves while in
case of immobile nutrients firstly on younger
leaves
Deficiency symptoms based on
physiological functions
• Nitrogen:
• Chlorosis: yellowing of leaves due to lack of chlorophyll.
Symptoms will first appear on older leaves
• Necrosis: necrotic spots will appear and destroy the
tissues
• Woody and cylindrical stem: Stem will appear woody and
cylindrical because N is involved in N metabolism of
carbohydrate. Due to deficiency of N these carbohydrates
are not being used and stored in stem that’s why
herbaceous plants sometimes show woody appearance
• Pinkish appearance of leaves: due to excessive
accumulation of anthocyanins because carbohydrates are
not being utilized in N metabolism, N is used in
accumulation of anthocyanins which give pinkish color to
leaves.
• Sulfur
• Deficiency symptoms are just like N because both are
constituent of amino acids
• Chlorosis: arises on the younger leaves because S is
immobile
• Retardation of cell division: suppression of fruit
formation
• Phosphorus:
• mobile element so symptoms will first appear on old
leaves
• Stunted growth of young parts and dark green coloration
of leaves (chlorophyll per unit area increases)
• Necrosis
• Production of cylindrical stem: Important physiological
function such as photosynthesis, respiration are
adversely affected due to shortage of P. All these
processes depend upon NADPH, ATPs etc all of which
contain P
• Silicon
• Plants become susceptible to lodging: Si is
constituent of cell wall. It gives strength to the cell and
when there is deficiency of Si, plant will fall.
• Plants become susceptible to fungal infections
• Boron
• Black necrosis of younger leaves: From base and
those of terminal buds
• Stiffness and brittleness of stem: stiff means hard and
brittle means easily breakable
• Loss of apical dominance: causes more branching of
the plant
• Inhibit cell division
• Fruits become fleshy and tubers may show necrosis and
breakdown of internal tissues
• Immobile and symptoms first appear on older leaves
• Potassium
• Marginal chlorosis/mottled: This marginal chlorosis
later on develops into necrotic spots at the leaf tips, at the
margins and between the veins because of the mobility of
K within the plant. The symptoms initially appear on
mature or older leaves
• Leaves may be curled
• Stem may be slender or weak with short internodes
• Roots of K deficient plant may be susceptible to fungi
which results in lodging of the plant
• Calcium
• Necrosis of young meristematic region i.e. tips of roots,
stem or leaves where cell division or wall formation is
high
• Chlorosis and backward hooking of leaves
• Roots appear brownish, short and highly branched
• Plants may be severely stunted if meristematic regions
die prematurely
• Magnesium
• Chlorosis between leaves veins: As Mg is a part of
chlorophyll so due to its deficiency there will be no
photosynthesis in older leaves. Due to extensive
deficiency whole leaf may become yellow or white
• Premature abscission of leaf
• Chloride
• Wilting of leaf tips
• General leaf chlorosis or necrosis
• Bronzing of leaves
• Roots may appear stunted and thickened near the tips
• Manganese
• Interveinal chlorosis with small necrotic spots. Mn is
mobile so initial deficiency will be on older leaves
• Also occur on younger leaves depending on plant
species
• Sodium
• Chlorosis or necrosis of leaves
• In some plants there is failure to form flowers particularly
in those where Na has an essential role
• Iron
• General chlorosis of young leaves due to immobility
• In case of prolong deficiency, veins may also become
chlorotic causing more leaves to turn white
• Zinc
• Reduces internodal growth and plants show rosette habit
(little leaves) due to close origin of leaves
• Small and distorted leaves
• Chlorotic leaves or development of white necrotic spots
because Zn is required for chlorophyll biosynthesis
• Copper
• Production of dark green leaves containing necrotic spots
firstly on young leaves
• Twisting of leaves
• Under permanent or extreme deficiency there is premature
abscission of leaves
• Nickel
• Marginal chlorosis
• Premature senescence
• Cupped leaves (mouse ear)
• Ni is part of urease enzyme in case of Ni deficiency, urease
enzyme will not be there resulting in accumulation of urea that
will cause leaf necrosis
• Molybdenum
• Co-factor nitrate reductase
• Chlorosis between the veins and necrosis of older leaves
• In some plants, the leaves may be twisted initially and die
later on
• No flower formation or there is premature flower abscission
Control measures
• Fertilizers
• To reduce or overcome nutrient deficiency,
fertilizers are used and can be applied as
foliar application or soil application
Control measures (fertilizer application)
Soil application
Foliar application
Macronutrients
Fertilizers
Inorganic
fertilizers
Organic
fertilizers
(humus)
Straight fertilizers (N/P/K)
Micronutrients
Compound
fertilizers
(mixed)
Application of fertilizers
• When soil is deficient to nutrient, we add a
particular nutrient.
• Analyze the soil and measure its nutrient
contents
• If there is deficiency of a particular nutrient, add
a particular fertilizer
• Fertilizer application types
• i) Soil application
• ii) Foliar application
Soil application
• These fertilizers are applied in the soil
• These include inorganic or organic fertilizers
• Most of the time macro or micro-nutrients are
added in soil
• NPK fertilizers are macro nutrients
• Based on the type of fertilizers, we categorize
them as
• a) Straight fertilizers
• b) Compound fertilizers
a) Straight fertilizers
• Those fertilizers which contain only one type of
nutrients are known as straight fertilizers e.g. N,
K, or P
• Super phosphate (to ameliorate P deficiency)
• Ammonium nitrate (N)
• Muriate of K (K)
b) Compound fertilizers
Those fertilizers which have two or more than two
nutrients in a specific ratio e.g. if a fertilizer
contains NPK then the ration will be 10, 14, 10
(N, P2O5, K2O)
Micronutrients
• No need to add
• Some time deficiency due to agricultural
practices
• Plants require micronutrients in very low
amount (mostly use their concentration in
micrograms)
• High amount will be toxic for plant growth
• Some plants require high quantity of
micronutrients e.g. rice requires high
amount of Zn for better growth so we use
ZnSO4
Organic fertilizers
• These are natural i.e. when leaves become
dead, they also become source of nutrients
because they have macro and micronutrients
• Adequate amount of organic fertilizer has better
effect on plant growth as compared to inorganic
fertilizer
• Organic matter decomposes – mineralization
• Mineralization depends upon many factors e.g.
temperature, water, availability of oxygen,
presence of micro-organisms, their types and
number
Foliar application
• Immediate remedy to recover deficiency
• If plants has been damaged seriously, nutrients can be
applied through leaves
• Nutrients in solution form are applied as foliar spray on
leaves and absorbed by leaves
• Certain conditions are required for absorbance through
leaves like use of surfactants
• Surfactants – these are reagents which reduce the
surface tension for maximum absorption. Among these
common are tween 80 (organic), tween 20 etc.
• Surfactants cause the breakdown of cutin on the surface
of leaves. Both cutin and waxes are hydrophobic in
nature and when this cuticle layer breaks, hydrophobic
property reduces and absorptions occurs through
epidermal cells
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Continue---• Stomata do not absorb foliarly applied solutions
because morphology of guard cells is in such a
way that outward flow of water is easy but
inward is not
• Effect of surfactant is not permanent
• Epidermal cells have genes which are involved
in continuous synthesis of cutin and waxes
• Epidermal layer is even broken down just by
touching the leaf surface
• So synthesis of cutin or waxes is continuous
process
Exogenous application
Application through one of the following way
1) Rooting medium
2) Pre-sowing seed treatment
3) Foliar application
Also known as shot-gun approach and its
effect is effective only for one generation
while for next generation again
application is required
Root mycorrhizae
• Mycorrhizae – a Greek word for “fungus and roots”
• Roots make an association with mycorrhizal fungi to
modify absorption nutrients
• 83% of dicotyledonous and 79% monocotyledonous
plants and all gymnosperms forms mycorrhizal
association
• Plants from families Brassicaceae or Cruciferae
(cabbage family), Chenopodiaceae (spinach family),
Proteaceae (macademia nuts) and aquatic plants rarely
have mycorrhizae
• Also absent from roots in very dry, saline or flooded soils
or where soil fertility is extreme i.e. high or low
Mycorrhizal fungi
• Composed of fine tubular filaments called
as hyphae which join to form fungal body
called mycelium
• There are two major classes of
mycorrhizal fungi
• 1. Ectotrophic mycorrhizae
• 2. Endotrophic mycorrhizae (vesiculararbuscular mycorrhizae)
Ectotrophic mycorrhizae
• These form a thick sheath or mantle
around the roots of plants
• Some mycelium penetrates between the
cortical cells
• Cortical cells are not penetrated by the
hyphae but are surrounded by the network
of hyphae called “Hartig net”
• Increase the absorption capacity of roots
particularly phosphorus
• Usually found in trees, woody
angiosperms, gymnosperms
Vesicular-arbuscular mycorrhizae
• They do not form compact mantle around the roots and
form less dense arrangement
• Extend outward in the soil
• About 10% of weight of root
• Penetrate in individual cells of cortex forming two types
of structures
• a) oval structures (vesicles)
• b) branched structures (arbuscules)
• Hence, the term vesicular-arbuscular mycorrhizae is
used
• Found in herbaceous plants
• Facilitate absroption of P and trace elements like Zn, Cu
• Plants have these mycorrhizae absorb 4 times higher P
in their roots as compared to non-assoiciated plants
Ion traffic into roots
• Membrane carriers, channels and pumps are
used to facilitate the transport of ions
• Transport proteins have two major classes
• 1) carrier proteins
• 2) channel proteins
• Carrier proteins (carriers, transporters, porters)
bind to particular solute to be trasnported
• Binding makes conformational changes in
carrier protein, which delivers the solute to other
side
• After release of solute, protein again reverts to
its original conformation and ready to pick up
another solute
Channel proteins
• Channel proteins form a charged-lined, waterfilled channel that extends across the membrane
• Diffusion through channel is dependent hydrated
size of ion because associated water molecule
must diffuse along with ion
• The number of ion channels discovered in plants
is increasing
• Currently there is solid evidence for K, Cl and Ca
channels
• Channel proteins are frequently gated i.e open
or closed
Electrogenic pumps
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Involved in active transport of ions
Against the gradient
Tightly coupled with metabolic energy
An important characteristic of pumps is
that they are reversible
• ATPase-proton pump