Transcript 02 Nutrition

Chapter 5
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Acquired primarily through the roots
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Inorganic ions
Nutrient cycles begin with plant roots –
mining minerals from the soil
Soil mycorrhizza & N-fixers assist
Research central to Ag and environmental
protection
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Crop plants utilize < 50% applied fertilizers
Leech into ground water (spoiling wells)
 Attached to soil particles (N availability)
 Contribute to air pollution
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OTOH ….. phytoremediation
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“intrinsic component in the structure or
metabolism of a plant or whose absence
causes severe abnormalities in plant
growth, development, or reproduction”
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C. HOPKiNS CaFe. Mighty good!
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(Macro- VS Micro-nutrients) VS Function
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1. Part of carbon compounds
a) Assimilated via ReDox rxns
2. Important in energy storage or structural
integrity
a) Typically as phosphate, borate, & silicate
3. Remain in ionic form
a) Enzyme cofactors & regulation osmotic potential
4. Involved in ReDox reactions
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Nutrient deficient solutions
Modified Hoagland – Complete Nutrition
Macronutrients: K, NO3, Ca, NH4, PO4, MgSO4
 Micronutrients: KCl, BO3, Mn, Zn, Cu, SO4, Mo, Fe
 Optional: Ni, Na, Si
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Typically characteristic symptomology
Occur simultaneously in different tissues
Defficiencies/excesses can induce
deficiencies/excesses in other nutrients
Viral infections mimic nutrient deficiencies
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Essential element mobile – old leaves first
Essential element non-mobile – young
leaves
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From the Hopkins text ….
Macronutrient – required in large amounts
In excess of 10mmole/kg of dry weight
 Generally involved in structure of molecules
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Micronutrients – small amounts
Less than 10 mmole/kg of dry weight
 Catalytic and regulatory roles like enzyme
acrivators
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Beneficial – not universal or not detectable
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Na, Si, Se, Co
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Na – essential for C4 plants
Si – 1-2% of dry matter Zea mays
Up to 16% (or more) of Equisetum
 Cell walls of grasses to help against lodging
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Co -- required for N-fixing bacteria
Se -- essential or tolerable?
Loco weeds! (up to 0.5%)
 Only grow in high Se environments
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Macro-/micro- versus functional
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Same nutrient often fills multiple roles!
Mg – component of chlorophyll; also enzyme
cofactor in ionic form
 Ca – component of cell walls; but also second
messenger
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Critical concentrations –
concentrations
measured in the tissues
below the level that gives
maximum growth
Nutrient limits growth
below critical
concentration
Toxicity can be observed
with micronutrients
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Sources and Uses
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Constituent of many macromolecules
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Slow stunted growth
Chlorosis of the leaves
Accumulation of anthocyanin pigments in stems/leaves
Excess N
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Absorbed in the form of NO3- and NH4+
Deficiency Symptoms
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Proteins, nucleic acids, some hormones, chlorophyll
Stimulates growth of the shoot system
Delays onset of flowering
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Sources and Uses
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Deficiency Symptoms
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Intense green leaves
Malformed leaves with necrotic spots
Accumulation of anthocyanin pigments
Excess
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Nucleic acid backbone; metabolism; membranes
Soil pH major role in availability
Organic phosphates converted to inorganic forms
Most commonly limiting nutrient -- mycorrhiza
Stimulates growth of roots
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Sources and Uses
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Activates enzymes; osmoregulation (stomates
in particular)
Deficiency Symptoms
Marginal chlorosis followed by necrotic lesions
 Increased suceptibility to root-rot
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Sources and Uses
Proteins (disulfide bridges), coenzymes (esp. A)
and vitamins
 Mustard oils in Brassicoids
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Deficiency Symptoms
Not a common problem; appropriate forms
produced by soil microorganisms
 General chlorosis including tissues around X/P
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Sources and Uses
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Important in cell division (mitotic spindle), cell
adhesion (middle lamella), & second messenger
Deficiency Symptoms
Appear in meristems
 Deformed and necrotic new leaves
 Poor root growth
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Sources and Uses
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Deficiency Symptoms
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Chlorophyll, reactions with ATP, and regulator
of enzyme activity
Chlorosis due to breakdown of chlorophyll
between veins
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Sources and Uses
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Of all micronutrients, required in largest amounts
Chlorophyll synthesis – but precise role is mystery!
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Deficiency Symptoms
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Enzymes not Fe-dependent
T&Z says chlorophyll-protein complexes
Loss of chlorophyll – intervenous spaces (serious leaves
turn white)
Degeneration of chloroplast
Multiple strategies for enhancing uptake
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Sources and Uses
Cell division, elongation, and integrity of cell wall
 Least understood
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Deficiency Symptoms
Structural abnormalities of cell walls
 Inhibition of both division and elongation in roots
 Cell division in shoot apex and young leaves inhibited
 Necrosis of the meristem
 Shortened internodes & enlarged stems
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Sources and Uses
Cofactor for oxidative enzymes
 Browning of apple and potato surfaces!
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Deficiency Symptoms
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Stunted growth, distortion of young leaves, and
loss of young leaves.
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Sources and Uses
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Activator for numerous enzymes
Deficiency Symptoms
Auxin metabolism
 Shortened internodes and smaller leaves
 Precise mechanism unclear!
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Sources and Uses
Enzyme cofactor
 Part of Oxygen-evolving complex
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Deficiency Symptoms
Aggravated by low pH and high organic content
 “Gray speck” in cereal grains
 Chlorosis between veins
 Discoloration and deformities in legume seeds
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Sources and Uses
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Key component of N metabolism
Deficiency Symptoms
In N-fixers can produce symptoms of N deficiency!
 Young leaves twisted and deformed
 Chlorosis and necrosis
 Highly species dependent
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Legumes, Brassicoids, and maize
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Sources and Uses
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Deficiency Symptoms
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Oxygen evolution and charge balance across
membranes
Reduced growth, wilting of leaf tips, chlorosis
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Sources and Uses
Not clear
 Ubiquitous in plant tissue – amt in seed sufficient!
 Studies – multiple generations of Ni-deficient plants
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Deficiency Symptoms
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Low germination rates (< 12%)
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increased Ni to 0.6 μM OR 1.0 μM -> 57% and 95%
Seedling vigor, chlorosis, necrotic lesions
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Micronutrients excellent examples of dangers
of excesses
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Critical toxicity level – 10% reduction in dry matter
Symptoms difficult to diagnose – excess of one
nutrient causes deficiency in another
Typically inhibit root growth
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