MINERAL NUTRITION
By
Fredeslinda C. Evangelista, PhD
ESSENTIAL ELEMENT one whose absence prevents a plant from
completing its life cycle
is part of some essential plant constituent or metabolite
One that has a clear physiological role
Essential elements Macronutrients- required in large
amounts (in excess of 10mmole/kg of dry weight)
Micronutrients- required in relatively small quantities (less than 30 mmole/kg of dry weight)
, O2
Nutritional Needs of Plants
Organic nutrition- production of carbon compounds i.e., incorporation of C,H,O via photosynthesis
Inorganic nutrition – acquisition of mineral elements from the soil
Mineral nutrients • Absorbed by roots
• Translocated to various parts of the plant
• Used in numerous biological functions
• Mycorrhizal fungi and nitrogen-fixing bacteria often participate with roots in the acquisition of nutrients
hydroponics Technique of growing plants with their roots
immersed in nutrient solution without soil
Requirements in hydroponics Maintenance of nutrient
concentration
Maintenance of pH
Sufficient supply of O2
In plant structure
Metabolism
Osmoregulation
Functions of essential elements
Symptoms related to the roles played by essential elements in plants
Mineral deficiencies
Mineral deficiencies More easily studied in hydroponic culture
than soil-grown plants: Deficiencies of several elements may occur
simultaneously Deficiencies or excessive amounts of one
element may induce deficiencies or excessive accumulations of another
Virus-induced plant diseases may produce symptoms similar to those of nutrient deficiencies
Functions of essential elements
Nitrogen (NO3-,
NH4+)
Required in greatest amounts
Constituent of amino acids, nucleic acids, chlorophyll, certain hormones (cytokinin, IAA)
Amino acid
Nitrogen Deficiency symptoms Chlorosis – yellowing of
leaves Growth inhibition Accumulation of
anthocyanin pigments in leaves, stem, petiole
Woodiness of stem Stimulates abundant growth
of the shoot
Essential elements
Essential elements
Sulfur (SO4-2)
Functions Found in two amino
acids Constituent of
several coenzymes (CoA) and vitamins (biotin, thiamine) essential for metabolism
Sulfur (SO4-2)
Functions Iron-sulfur protein (Fd) important in electron
transport in photosynthesis
Essential elements
Sulfur (SO4-2)
Deficiency symptoms Chlorosis Anthocyanin accumulation Stunting of growth Develops in young mature leaves
(immobile element)
Essential elements
Phosphorus (H2 PO4
-, HPO4
-2) Functions Component of
important compounds of the cell sugar-phosphate
intermediates of respiration and photosynthesis
Essential elements
Phosphorus (H2 PO4
-, HPO4
-2) Functions Component of important
compounds of the cell Phospholipids ATP
Essential elements
Phosphorus (H2 PO4
-, HPO4
-2) Functions Component of important
compounds of the cell Nucleic acids
Essential elements
Phosphorus (H2 PO4
-, HPO4
-2) Deficiency symptoms Stunted growth With necrotic spots Dark green coloration of leaves May produce excess anthocyanin Production of slender but not woody stems Death of older leaves
Essential elements
Boron (H3BO3) Evidence suggests that it plays a role in: Cell division and elongation in the root Nucleic acid synthesis Hormone responses Membrane function
Deficiency symptoms Black necrosis of young leaves’ base and
terminal buds Unusually stiff and brittle stem
Essential elements
Boron (H3BO3) Deficiency symptoms Apical dominance may be lost Fruits, fleshy roots and tubers may exhibit necrosis or
abnormalities
Potassium (K+) Functions Plays a role in regulation of osmotic potential of cells Activates many enzymes involved in respiration and
photosynthesis
Essential elements
Potassium (K+) Deficiency symptoms Marginal chlorosis Necrosis at leaf tips, margins and between
veins Curled and crinkled leaves Slender and weak stems with abnormally
short internodes
Essential elements
Potassium (K+) Deficiency symptoms Susceptible to root-rotting fungi present in
the soil Prone to lodging Calcium (Ca+2) Functions Used in the synthesis of new middle
lamella Used in mitotic spindle during cell division Needed for normal functioning of the
plasma membrane
Essential elements
Calcium (Ca+2) Functions Acts as a second messenger to responses
to environmental and hormonal signals
Essential elements
Calcium (Ca+2) Deficiency symptoms General chlorosis Necrosis of young meristematic regions such
as tips of root s and young leaves Root system may appear brownish, short,
highly branched and slippery to touch Severe stunting if tips die prematurely
Essential elements
Magnesium (Mg+2) Role in activation of
enzymes involved in respiration, photosynthesis and the synthesis of DNA and RNA
Part of the structure of chlorophyll
Essential elements
Magnesium activates Rubisco
Magnesium activates PEPcarboxylase
Magnesium (Mg+2) Deficiency symptoms Chlorosis between veins Leaves may become
yellow or white Premature leaf abscission
Essential elements
Chlorine (Cl-)
Functions Required for water-splitting reaction of photosynthesis through which O2 is formed
Chlorine (Cl-) Functions Required for cell division in both roots and
leaves Osmotically active solute in the vacuole Major counterion, maintaining neutrality
across membranes Deficiency symptoms Develops wilting of leaf tips Chlorosis and necrosis of leaves
Essential elements
Chlorine (Cl-) Deficiency symptoms Leaves exhibit reduced growth Bronzing of leaves Roots appear stunted and
thickened near the root tips
Essential elements
Manganese (Mn+2)
Functions Activates several
enzymes (decarboxylases and dehydrogenases) involved in Krebs cycle
Essential elements
Manganese (Mn+2) Functions Involved in photosynthethic reaction through
which oxygen is produced from water Deficiency symptoms Intervenous chlorosis associated with
development of necrotic spots
Essential elements
Iron (Fe+2, Fe+3) Functions Component of
enzymes involved in the transfer of electrons (redox reactions e.g.,cytochromes)
Essential elements
Iron (Fe+2, Fe+3) Functions Constituent of several oxidase (peroxidase,
catalase) Required in the synthesis of chlorophyll Deficiency symptoms Intervenous chlorosis Symptoms appear first in young leaves Whole leaf may become chlorotic
Essential elements
Essential nutrients
Maintaining availability of Fe Use of chelators
such as EDTA
Strategies for uptake under conditions of iron stress
Zinc (Zn+2) Functions Activates some
enzymes (e.g., alcohol dehydrogenase)
Required for chlorophyll biosynthesis of some plants
Essential elements
Zinc (Zn+2) Deficiency symptoms Intervenous chlorosis then white, necrotic spots Reduction in internodal growth with small, distorted leaves with leaf margins having a puckered
appearance
Essential elements
Copper (Cu+2) Functions Associated with enzymes involved in redox
reactions (e.g. plastocyanin, cytochrome oxidase)
Deficiency symptoms Dark green leaves with necrotic spots Twisted leaves Leaves may abscise prematurely
Essential elements
Nickel (Ni+2) Functions Required for activity of enzyme (e.g., urease) Suggested to play a role in the mobilization of
nitrogen during seed germination and seedling growth
Deficiency symptoms Leaf tip necrosis due to accumulation of urea Reduced germination of seeds (legumes and
cereals)
Essential elements
Nickel (Ni+2) Deficiency symptoms Depressed seedling vigor, chlorosis and
necrotic lesions in leaves Flower formation may be prevented or abscise
prematurely
Essential elements
Molybdenum (MoO4-2)
Functions Component of several enzymes (e.g. nitrate
reductase and nitrogenase) Nitrate reductase converts nitrate to nitrite Nitrogenase converts nitrogen gas to ammonia in
nitrogen-fixing microorganisms Deficiency symptoms Interveinal chlorosis Necrosis of older leaves Whiptail disease in broccoli and cauliflower
Essential elements
Beneficial elements
Additional requirements of some plants Sodium Silicon Selenium Cobalt
Sodium (Na+) Functions Required in species utilizing the C4 and CAM
pathways of carbon fixation to regenerate PEP
Stimulates growth of C3 plants by enhanced cell expansion
Can partially substitute for K+ as an osmotically active solute
beneficial elements
Deficiency symptoms
Chlorosis and necrosis Failure to form flowers
Beneficial elements
Cobalt (Co) Functions Required by nitrogen-fixing bacteria
Free living Symbiotic
Essential for growth of legumes When legumes are provided with fixed nitrogen,
cobalt is no longer required
Silicon (Si) Functions Required only by members of family Equisetaceae Other plants showed enhanced growth and fertility Can ameleorate the toxicity of many heavy metals
Deficiency symptoms Prone to lodging and fungal infection
Beneficial elements
Beneficial elements
Selenium (Se) Generally toxic to most plants High concentrations tolerated by members of
the legume genus Astragalus Thought to be essential to these plants
Soil Consists of: Solid phase
Mineral particles derived from parent rock Primary source of nutrient elements
Organic materials in various stages of decomposition
Liquid phase- water/ soil solution Gases Variety of microorganisms
Soil When soil is stirred in water
Sand Silt Clay – remain in stable suspension
Colloid -small enough to remain in suspension
and too large to go into true solution - will scatter light –Tyndall effect
- 2 phase system (solid i.e. colloidal micelle suspended in liquid )
settle
Colloidal clay Exposes large surface area Surface with numerous negative charges
Can bind and retain cations Can exchange cations
Negative charge on the surface Mineral colloid (clay i.e. aluminum silicates)
simplest type kaolinite Al2Si2O5.(OH)4
Charge due to ionization of alumina and silica at the edges
Negative charge on the surface Organic colloid (Humus)
Incompletely degraded to colloidal dimensions
Largely derived from lignin and carbohydrates
Negatively charged because of the dissociation of H+ ions from carboxylic acid, hydroxyl and phenolic groups
COOH + OH- = COO- + H2O
Colloidal clay
Highly hydrated Positive pole of water attracted to
negatively charged surfaces Negative charge and hydration contributes to
stability of colloidal suspension
Attract cations from surrounding soil solution Al+3>H+>Ca+2>Mg+2>K+=NH4
+>Na+ Trivalents> divalents>monovalents Electrostatic rules are modulated by relative
hydrated size
Colloidal clay
Cation adsorption is reversible Ion exchange -exchange between cation
adsorbed and cation in soil solution Exchangeability- ease of removal Cation with higher affinity can displace an ion
lower in the series (H+ > Ca+2) An ion of lower affinity can, by mass action,
displace an ion of higher affinity
Colloidal clay
Plant source of mineral nutrients Cations Immediate source – soil solution Nutrient reservoir- adsorbed ions
Not easily lost when leached by water Roots normally secrete H+ ions which
assist in the uptake of nutrients
Anions Soil colloids do not attract anions Remain in soil solution
Root-microbe interaction
Association with mycorrhizal fungi Mycorrhizae – a root infected with fungus
Mycelia –the body of a fungus made up of a mass of hyphae
Facilitates uptake of nutrients e.g., phosphorus beyond the depletion zone
Nutritional status of the host plant is a key factor in extent of mycorrhizal association
Nutrient depletion zone defines the limit of the soil from which the root is able to readily extract nutrient elements
2 types: 1. Ectotrophic mycorrhizal fungi- with thick mantle of
mycelium around the roots, between cortical cells (Hartig net) and into the soil Infect tree species exclusively Uptake of P may be by simple diffusion
3. Vesicular- arbuscular mycorrhizal fungi- less dense hyphae grow within the root and the surrounding soil
Association with most species of herbaceous angiosperms
Uptake of P may be by simple diffusion from intact or degenerating arbuscules
Root-microbe interaction
Bacteria Induces formation of proteiod roots (intense
lateral root production) Allow intensive mining of soils for poor mobile
nutrients like phosphorus Could be related to IAA production by the bacteria
Both invasive and free living nitrogen-fixing bacteria are the primary source of nitrogen for plants
Root-microbe interaction
dinitrogenase
Nitrosomonas Nitrobacter