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Mineral Nutrition, Individual Nutrients, Study: - Coggle Diagram

- - - - lateral branches often smaller than primary root
      - includes sugarbeet, alfalfa, carrot
      - main root is discernable
    - - initially 3-6 primary roots
      - nodal (adventitious) roots branch off primary root
      - fibrous network with similar diameter roots
      - includes wheat, grasses
  - - - quiescent center is reservoir of meristematic cells surrounded by initial cells
      - initials rapidly divide to produce new cells
    - - protects apical meristem from physical damage during growth
      - site of gravity perception
      - secretes mucigel sheath
        
        lubrication for root growth through soil
        
        hospital environment for symbiotic organisms
    - - phloem develops first (carbohydrate supply to growing tips)
      - xylem develops later (water and mineral transport to plant)
      - endodermis rings stele
    - - epidermal extensions that contact soil
      - comprises about 60% of total root surface area
      - primary site of water and mineral uptake by roots
  - - - Ca2+ absorbed at root tip
      - Fe absorbed all along root surface
      - NH4+ absorbed in elongation zone
      - most minerals absorbed by root hairs
    - - root apex and root hairs grow into nutrient-rich areas of soil
        
        nutrient depletion zones develop around root
        
        low nutrient load, big zone
        
        high nutrient load, small zone
        
        depletion requires continuous growth
        
        minerals move in soil by bulk flow
    - - growth depends on mineral availability
        
        low minerals = low growth (mineral limited)
        
        adequate minerals = increased growth
        
        excessive minerals = decreased growth (carbohydrate limited)
      - Resource allocation
        
        in soils that exceed optimal mineral requirements, fewer roots are needed to supply shoot
        
        favors shoot growth over root growth
  - - - acids mineralize rock
      - allelopathic agents reduce resource competition
      - chemoattractants recruit beneficial organisms into symbiotic relationships
  - - - found in 83% of all dicots
      - found in 70% of all monocots
      - found in all gymnosperms
    - - plant provides carbohydrate to fungi
      - fungi aids mineral uptake from soil of Pi, Zn, Cu
      - fungi provide pathway for carbohydrates and signaling molecules to move between trees
    - - hartig network invades cell walls surrounding cortical cells
      - mainly found in temperate species
      - vasicular-arbuscular mycorrhizae invade cell lumen
      - arbuscules release nutrients to plant (esp Pi, Zn, Cu)
      - hostorium
        
        plasma membrane-bound structure that houses fungus within plant cell lumen
- - - - Liquid phase, which contains dissolved minerals for uptake
      - Gas uptake, which occurs from gas phase and not from dissolved gases
      - solid phase, which acts as reservoir for minerals
    - - plant roots
      - microbes, including bacteria and fungi
      - animals
  - - - breakage due to freezing, shifting in earth's curst, etc
      - wearing caused by sand in air and water
      - chemical dissolution due to minerals in solution or plant secretions of acids
    - - breakdown of plant and animal remains by bacteria and fungi
      - complex molecules broken down into smaller, simpler forms
      - adds minerals to upper layers of soil
    - - organic compounds released by plants increase flocculation*
  - - - percolation of water downward
      - carries minerals, organics, particles, etc
      - minerals removed from upper layers of soil
  - - - averages 30-60 cm deep
      - usually acidic (pH <7)
      - dark color due to organics
      - richest in plant nutrients
    - - averages 60-90 cm deep
      - usually neutral pH (pH = 7)
      - rich in plant nutrients
    - - depth varies depending on underlying rock and geology of region
      - formed from bedrock or parent material of earth's crust
      - sedimentary rock contributes 50% N needed by plants
      - igneous rock contributes little N to plants
  - - - layer >30 cm thick that contains >30% organic matter
      - includes bogs, peat, mucks
      - relatively rare soil type
    - - most common soil type
      - contains 2-5% organics
      - mainly composed of sand, silt, and clay
    - - mineral soils with poor nutritional value
      - low organic matter (<2%)
  - - - 3.5-5.0: coniferous forests
      - 4.5-6.0: azaleas, camellias
      - 6.0-7.5: deciduous forests, crop fields
      - 7.5-9.1: arid, alkaline flats--few plants
      - 3.2-4.6: bogs
    - - root growth favors soil pH 5.5-6.5
        
        secrete acids or compounds that form acids in soil
        
        acids promote weathering of soils
        
        increases solubility of carbonates, phosphates, and sulfates
      - leaching removes minerals from upper layers of soil
      - alkaline soils
        
        lack of rainfall inhibits leaching, causing minerals to accumulate
  - - - surface of soil particles negatively charged
      - cations bind soil particles by ionic attractins
      - cations displaced by other cations (ie, cation exchange)
      - higher capacity is better
    - - most anions remain in solution (like charges repel)
    - - very low abundance compared to negative charges
- - - - grow plants in nutrient poor substrate
        
        gravel
        
        vermiculite
        
        perlite
        
        expanded clay
        
        rock wool
        
        sand
      - nutrient solution flushed through medium
      - medium removed by leaching
  - - - roots in liquid medium
      - aeration required
      - roots protected from light
      - advantages
        
        medium strictly defined
        
        medium easily manipulated
      - disadvantages
        
        large volumes of liquid medium
        
        medium changed frequently
        
        depletion of nutrients
        
        bacterial and algal growth
        
        disposal of used medium
      - Growth without soil
      - Used commercially and for controlled nutrient studies
    - - nutrient film growth system
        
        roots in tray or embedded in inert material (eg rockwool, vermiculite)
        
        thin film of medium passed over roots
      - advantages
        
        reduces volume of medium
        
        medium filtered and recycled
        
        movement provides aeration
      - Disadvantages:
        
        may restrict root growth
      - used commercially and form controlled nutrient studies
    - - roots suspended in air
      - continuously sprayed (misted) with medium
      - advantages:
        
        easy manipulation of gaseous environment
      - Disadvantages
        
        required higher levels of minerals than hydroponics and nutrient film systems to sustain rapid growth
      - not widely used commercially and for controlled nutrient studies
    - - Medium periodically rises to immerse roots, then recedes
      - advantages: roots exposed to moist atmosphere
      - disadvantages:
        
        required higher levels of minerals than hydroponics and nutrient film systems to sustain rapid growth
      - Not widely used commercially for controlled nutrient studies
  - - - contains all essential elements
        
        may eliminate specific element
        
        highest level without toxicity
        
        sustains rapid growth
        
        minimize nutrient depletion achieved by:
        
        using dilute solution
        
        Changing solution often
        
        N supplied as NH4 and NO3
        
        pH rises rapidly when only NO3 used
        
        maintains cation/anion balance
      - Combining stocks
        
        macronutrients are added separately to prevent precipitation
        
        a combined micronutrient stock, excluding Fe
        
        iron added in chelated form
        
        NaFe DTPA
        
        NaFe EDTA
        
        Chelators:
        
        maintaining Fe in Solution is a problem
        
        Fe tends to oxidize in air
        
        Fe3+ precipitates out of solution
        
        Fe3+ not available to plant
        
        Chelators keep Fe in Solution
        
        form soluble complex with Fe
        
        release Fe at root surface
        
        Common Chelators:
        
        DPTA
        
        EDTA
        
        nickel contaminates other chemicals and may not need to be added
- - - - 50% used by plant
      - 50% leached, leading to groundwater contamination
  - - - H, C, O not considered essential mineral elements
        
        Plants accumulate other minerals such as Al, Se, Co
        
        improve growth or bacterial association
        
        not essential for plant growth and development
        
        required by some plants, but not generally required
    - - Group II: Minerals important in energy storage, or structural integrity
        
        includes P, B, and Si
      - Group III: Minerals that remain in ionic form
        
        members act as constituents of important enzymes or creating ionic gradients across membranes to impact osmosis
        
        includes K, Na, Mg, Ca, Mn, Cl
      - Group I: Minerals that from organic compounds
        
        includes N and S
      - Group IV: Minerals involved in electron transfers
        
        includes Fe, Cu, Zn, Mo, Ni
- - - - required for osmoregulation
    - - required for cell wall integrity
  - - - required for wall integrity
    - - required for photosynthesis
    - - temporary storage pool
- - - - incorporation of OH and H onto C at C=C sites
      - common reaction in metabolism
  - - - both O atoms incorporated into 1 or 2 organic molecules
      - ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco)
        
        both O atoms incorporated into 1 organic molecule
        
        most common oxygenase in plants
        
        3-PGA metabolized by C3 photosynthetic pathway
        
        2-phosphogylcolate metabolized by photorespiratory pathway
        
        also incorporates O via H2O
      - lipoxygenase
        
        both O atoms incorporated into 1 organic molecule
        
        oxidation of fatty acids
      - prolylhydroxygenase
        
        O atoms incorporated in 2 organic molecules
        
        effects posttranslational modification in ER
    - - 1 O atom incorporated into organic compound
      - 1 O atom incorporated into H2O
      - aka mixed function oxygenase
      - requires NAD(P)H as electron donor
      - localized in ER
      - variety of substrates
        
        monoterpenes
        
        diterpenes
        
        fatty acids
      - ex: cytochrome
- - - - deficiency symptoms first appear in older leaves (older leaves sacrificed to produce new leaves)
  - - - deficiency symptoms first appear in younger, developing leaves
- - - - excessive minerals = saline
        
        Na and Cl most common
        
        problem is no rainfall (inhibits leaching)
        
        irrigation adds salt to soil
        
        heavy metal accumulation
        
        leads to salinity stress
        
        Group IA = halophytes
        
        growth stimulation with Cl- < 400 mM
        
        includes sea blite, salt blush
        
        tolerate saline conditions via exclusion, excretion, and sequestration
        
        Group IB = halophytes
        
        tolerant, but growth retarded
        
        townsends cordgrass, sugar beet
        
        Group II = halophytes and nonhalophytes
        
        halophytes include red fescue, puccinellia peisonis
        
        nonhalophytes include cotton, barley, tomato, common bean, soybean
        
        not tolerant of salt
        
        Group III = very salt-sensitive nonhalophytes
        
        killed or severely inhibited by salt
        
        includes fruit trees
    - - plant tissue analysis is required for each mineral in different tissues at each growth stage to determine adequate levels
- - - - leaching from soil by water movement
      - sale of produce or livestock
    - - addition of inorganic fertilizers
        
        straight fertilizer (N, P, or K)
        
        mixed fertilizer (N, P, and K)
        
        may add other nutrients
      - addition of organic fertilizers
        
        decompose in soil (mineralization)
        
        "slow release" fertilizer
        
        rate of release is variable
        
        termperature-dependent
        
        bacterial and fungal activity
        
        enhances water retention and drainage in soil
        
        good soil fertility requires 5% organic matter
      - Adjustment of soil pH is critical
        
        pH affects mineral availability in soil
        
        pH/mineral chart P33
        
        line thickness represents nutrient availability
        
        each nutrient is affected differently
        
        Optimum soil pH: 5.5
        
        To increase soil alkalinity (increase pH), lime or dolomite is added
        
        To increase soil acidity (decrease pH), sulfur compounds or (NH4)2SO4
      - Foliar application effective as "quick fix"
        
        decreased lag between applications and uptake for Fe, Cu, Mn, etc
        
        applied as thin film on leaf surface
        
        nutrients diffuse across cuticle
        
        salt accumulation leads to burns or scorching
        
        good technique for tree crops and grapes
        
        increased protein content in wheat seeds if applied late in growing season
- - - - requires ten electrons
      - 25% of total energy expenditure in shoots and roots
      - 2% of plant DW
    - - source of reductant (ex Fd, thioredoxin, NADH, NADPH)
      - aka photoassimilation
        
        occurs only when PET > C3 cycle
        
        increased CO2 = decreased photassimilation
        
        decreased CO2 and increased light = increased photoassimilation
        
        C4 plants: photoassimilation occurs in mesophyll cells ( in decreased Co2)
- - - - in the presence of O2, Fe2+ (which has higher solubility) becomes Fe3+ (which has lower solubility)
    - - Fe(OH)2+
      - Fe(OH)3
      - Fe(OH)4-
      - Fe(OH)2PO4
    - - soil acidification
      - release of chelators
        
        malate, citrate, phenolics, pisidic acid
        
        chelators form stable electrostatic complexes with Fe3+
        
        common in dicots (pea, tomato, soybean)
      - release of phytosiderophores
        
        phytosiderophores contain amino acids not found in proteins (avenic acid, mugineic acid)
        
        Fe3+ siderophore complex soluble in soil solution
        
        common in monocots (barley, maize, oat)
        
        action:
        
        Fe3+ siderophore uptake system
        
        under Fe-Deficiency
        
        increased siderophore extrusion
        
        increased Fe3+ siderophore uptake
      - reduction of iron
        
        iron-chelate reductase
        
        reduces Fe3+ to Fe2+
        
        electron donor: NAD(P)H
        
        Activity increases under Fe deficiency
    - - soil acidification increases Fe3+ solubility
        
        H+ NH4+ antiport
        
        acid secretion (malic acid, citric acid)
      - Iron deficiency stimulates H+ extrusion
  - - - citrate
      - nicotianamine
    - - cytochromes
        
        iron is component of heme
        
        cytochrome cofactor
        
        enzyme-mediated redox reactions
        
        ferrochetalase inserts Fe into porphyrin ring
      - Fe-S protein of redox chains
      - iron-sulfur centers
        
        cofactors:
        
        Fe2S2
        
        Fe4S2
        
        electron transfer reactions
        
        photosynthetic electron transport
        
        mitochondrial electron transport
      - phytoferritin
        
        free Fe reacts with O2
        
        forms superoxides
        
        degrades lipids in membrane--Fe must be quickly incorporated into organic compounds or sequestered
        
        Fe released by proteolysis
- - - - urease
      - coenzyme A
    - - Nod factors
      - alliin in garlic (antiseptic)
      - sulforaphane in broccoli (anticarcinogen)
  - - - predominantly released by soil weathering
      - H+ - SO4 2+ symporter
    - - atmospheric reactions
      - acid rain
      - SO2 and H2S may enter leaves via stomates
      - toxic exposure
  - - - oxidation state of S: +6 to -4
        
        requires 10 electrons per molecule
        
        electron donors: GSH, Fd, NAD(P)H, O-acetylserine
        
        photosynthesis provides Fdred
        
        photorespiration provides serine
    - - SO2 2- --> O-sulfated metabolites
        
        sulfate activation
        
        sulfation
        
        O-sulfated metabolite synthesis
        
        synthesis of metabolites:
        
        sulfotransferases transfer SO4 2- from PAPS to various molecules (choline, brassinosteroids, flavanol, gallic acid glucosides, glucosinolates, peptides, polysaccharides)
      - SO4 2- --> Cysteine
        
        sulfate activation
        
        APS reduction occurs in plastids
        
        cysteine synthesis
        
        S-containing amino acid uses
        
        cysteine and methionine used in many biosynthetic pathways
        
        proteins
        
        acetyl-CoA
        
        S-Adenosylmethionine
        
        ethylene
        
        CH3 Transfers
    - - sulfate activation
        
        SO4 2- is very stable
        
        formation of APS
      - ATP sulfurylase
        
        unfavorable reaction, so APS and PPi rapidly removed
        
        multiple forms:
        
        plastidic (major)
        
        cytosolic (minor)
      - Sulfation
        
        APS kinase adds phosphate to APS to form PAPS
        
        occurs in cytosol
- - - - H+ cation antiport in form of H+ - NH4+ antiport
      - acid secretion
        
        malic acid
        
        citric acid
  - - - chemiosmotic ATP synthases in chloroplast and mitochondria
      - substrate level phosphorylation
        
        glyceraldehyde3-phosphate dehydrogenase (glycolysis)
        
        succinyl-CoA synthase (TCA cycle)
    - - sugar phosphates
      - phospholipids
      - nucleotides
- - - - dissipates transmembrane H+ potentials
      - plants sequester NH4+ in vacuole
    - - Toxicity:
        
        increased NO3- is toxic to animals
        
        methemoglobinemia and nitrosomines pose issues
        
        high levels of NO3- not toxic to plant
      - processes in plants:
        
        nitrate reductase (NR)
        
        components:
        
        holoenzyme: 100kD homodimer
        
        prosthetic groups: FAD, heme, Mo, Pterin
        
        two active sites per complex
        
        main Mo compound in plants
        
        reaction mechanism:
        
        occurs as a series of electron transfer reactions
        
        NAD(P)H --> FAD (2 electrons transfered)
        
        FAD --> Heme
        
        Heme --> Mo
        
        Mo --> NO3- to yield NO2-
        
        located in cytosol
        
        inactivated by protein phosphorylation, with phosphorylation occurring in the dark due
        
        expression induced by NO3-, light, carbohydrates
        
        Nitrite reductase (NiR)
        
        components:
        
        holoenzyme: 63 kD monomer
        
        prosthetic groups: FAD, Fe4S4 cluster, heme
        
        Reaction Mechanism
        
        Transfer of 6 electrons through NiR
        
        PSI --> Fd
        
        Fd --> Fe2S4 center
        
        Fe4S4 center --> heme
        
        Heme --> NO2- to yield NH4+
        
        location: chloroplast
        
        nuclear gene product imported into chloroplast (transit sequence)
        
        No2- produced by NR in cytosol moves to chloroplast
        
        Regulation:
        
        induced by NO3-, light, sucrose
        
        repressed by asparagine, glutamine
      - Site of Nitrate assimilation
        
        occurs in both shoots and roots
        
        site depends on NO3- supply and plant species
        
        NO3- concentration in soil
        
        decreased NO3- leads to assimilation occurring in roots
        
        increased NO3- leads to assimilation occurring in shoot
        
        plant species:
        
        temperate plants tend to assimilate in roots
        
        tropical plants tend to assimilate in shoots
        
        assimilation in roots:
        
        NH4+ assimilated into organic molecules
        
        specific organic N depends on species
        
        amino acids
        
        amides
        
        ureides
        
        organic N--> metabolism and transport
      - GS-GOGAT System: a 2-enzyme system
        
        Two enzyme system:
        
        GOGAT = glutamine:2-oxoglutarate aminotransferase = glutamate synthase
        
        Types of GOGAT enzymes:
        
        NADH-GOGAT
        
        regulation: activity induced by increased glutamine
        
        Fd-GOGAT
        
        holoenzyme: 165 kD
        
        when located in chloroplasts
        
        2 more items...
        
        gene regulation:
        
        2 more items...
        
        location: plastids of non-photosynthetic tissues
        
        roots (NH4+ assimilation from rhizosphere)
        
        vascular bundles of developing leaves
        
        synthesizes glutamine transported from roots or senescing leaves
        
        GS = glutamine synthetase
        
        Forms:
        
        plastidic forms
        
        shoot chloroplasts
        
        2 more items...
        
        root plastids--local consumption
        
        induction of GS gene expression
        
        regulation: increased by light and carbohydrate
        
        cytosolic form
        
        increased in germinating seeds and vascular tissue
        
        induction of GS gene expression
        
        regulation--light and carbohydrates have no effect
        
        Glutamine synthase
        
        8 nearly identical subunits
        
        prosthetic group (only 1): Mg2+, Mn2+, or Co2+
        
        holoenzyme: 350 kD
        
        methionine sulfoxide
        
        specific inhibitor of GS
        
        blocks all incorporation of NH4+
        
        rapidly incorporates NH4+ into amino acids to avoid NH4+ toxicity
        
        Transaminases
        
        transfer N from glutamate or glutamine to form other amino acids
        
        Cofactor: Vit B6
        
        amino acid biosynthesis in chloroplast
        
        14CO2 rapidly incorporated into AAs (glutamate, aspartate, alanine, serine, glycine)
        
        includes aspartate aminotransferase (ATT)
        
        -NH2 of Glu transferred to carboxyl atom of Asp
        
        role of aspartate in plant leaves
        
        shuttles reducing equivalents
        
        mitochondria to cytosol
        
        chloroplast to cytosol
        
        transport of C from mesophyll to bundle sheath cells in C4 photosynthesis
      - GDH System
        
        Glutamate dehydrogenase (GDH)
        
        reversible enzyme
        
        possible alternative route for assimilating NH4+
        
        cannot substitute for GS-GOGAT system
        
        GS and Fd-GOGAT mutants survive only under conditions that minimize photorespiration
        
        methionine sulfoxide acts as specific inhibitor of GS and blocks all incorporation of NH4+ into glutamate
        
        primary function: deanimation of glutamate
        
        isozymes:
        
        NADH-GDH in chloroplast
        
        NADH-GDH in mitochondria
  - - - energy-sufficient conditions --> Glu + Gln (C-rich)
      - energy-limiting conditions --> Asn (N-rich)
  - - - most N-fixing bacteria are free-living in environment
      - some N-fixing bacteria form symbiotic relationships
      - relationship with plants:
        
        plants supply bacteria with:
        
        carbohydrate energy source
        
        other nutrients
        
        organism creates microaerobic (minimal O2) environment
        
        high respiration rates
        
        photosynthetic O2 evolution during the day, N-fixation at night
        
        bacteria provide plant with reduced N (NH4+)
        
        specializes structures create internal anaerobic environment in presence of O2
        
        root nodules
        
        symbiosis between legumes and rhizobia
        
        most common N-fixing association
        
        N-fixation in specialized structures known as root nodules that sequester bacteria from plant
        
        membranes derived from plant PM
        
        nodules induced by bacteria
        
        morphology:
        
        2 more items...
        
        legume/bacterial infection specificity
        
        establishment of symbiosis
        
        symbiosis is not obligatory
        
        2 more items...
        
        N-limiting conditions induce symbiosis
        
        3 more items...
        
        in gunnera, existing stem gland develops into nodule independent of bacteria
        
        in grasses:
        
        pseudosymbiotic association with N-fixing bacteria
        
        bacteria anchored in root surface at elongation zone and root hairs
        
        regulation of oxygen levels
        
        gas permeability regulated in root nodules
        
        maintain O2 sufficient to support respiration, but not inactivate nitrogenase
        
        increased gas permeability in presence of light, drought, NO3-
        
        leghemoglobin binds O2 in root nodules
        
        plant synthesizes globin subunit
        
        bacteria synthesizes heme cofactor
        
        facilitates O2 diffusion to respiring bacteria
        
        2 more items...
        
        heterocysts
        
        cyanobacteria contain heterocysts (thick walled cells)
        
        formed when deprived of NH4+
        
        cells lack PSII and do not generate O2
        
        not formed in all cyanobacteria
        
        require anaerobic conditions to fix N (such as flooded fields, rice paddies)
        
        cyanobacteria as fertilizer
        
        cyanobacteria fix N when flooded
        
        as soil dries, cyanobacteria die
        
        as cyanobacteria die, nutrients released to soil
        
        N2-Fixing prokaryotes release NH3 to plant
        
        plant converts NH3 into organic compounds
        
        organic N transported by plant
        
        classes of organic N transporters in legumes:
        
        Amide transporters
        
        principally asparagine and glutamine
        
        temperate-region legumes such as pea, clover, broadbean, lentil
        
        Ureide transporters
        
        principally allantoic acid, allantoin, citrulline
        
        3 more items...
        
        tropical-region legumes such as soybean, kidney bean, peanut, southern pea
      - N-fixing bacteria function in (nearly) anaerobic conditions
  - - - change in Gibbs free energy = -27 kJ mol -1
      - activation energy to overcome triple bond N-N is high
      - biological cost: 12 g C per 1 g N2 fixed
      - reduction of H+ to H2 competes with N2 fixation
        
        30%-60% of energy lost as H2
        
        hydrogenase splits H2 to recover electrons for N2 fixation
    - - acetylene reduction used as comparative assay for N2 fixation
        
        GC method: 2 electrons per acetylene reduced versus 4 electrons per N2 reduced
        
        reduces gas diffusion in and out of nodule
        
        stimulates microorganisms to release ethylene
      - direct measurement of N2 requires MS method
    - - subunits--Fe Protein and Mo Protein
        
        Fe-Protein
        
        very sensitive to O2
        
        4Fe-4S dimer
        
        MoFe-Protein
        
        tetramer
        
        2 Mo atoms per molecule
        
        2 Fe-S clusters, each associated with Mo atom
        
        variable number of Fe-S clusters
        
        sensitive to O2
    - - reaction mechanism
        
        Fdred donates electrons to Fe-Protein
        
        Fe-Protein donates electron to Mo-Protein
        
        Mo-Protein reduces N2 to NH3