Bio121 Mineral Nutrition 2

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