Dr' Bennett copy

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CHAPTER 5 MINERAL NUTRITION
Autotrophic Organism which can synthesize all
its growth constituents from the basic elements.
CO2, H20, essential mineral elements (inorganic)
Photolithotropic essential components of
growth are synthesized in the presence of light
from inorganic or lithic (soil) elements.
Essential Elements (criteria) 1. If plant
fails to grow and complete its life cycle in
a medium devoid of the element. 2. If it is a
constituent of a necessary metabolite (i.e.,
a part of an amino acid, etc.).
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Sodium, Silicon, Cobalt essential in some
plants, only
Atriplex Rice Sugarcane lower plant forms-

(N)-fixing organisms
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Plant Nutrients
On a per hectare basis (2.47 acres ha-1) Macro
nutrients required 10 to 100 kg
ha-1 Micronutrients
grams ha-1 C, H, O tons ha-1
- Nutrients enter the plant as ions, whether
the fertilizer source is organic (i.e., manure)
or inorganic (commercial fertilizer).
- All chemical elements in plants come
from Soil Water Atmosphere
biosphere
- Nutrients in the biosphere are continually
being re-cycled - Sewage sludge use for
fertilizers is sometimes limited because of high
concentration of heavy metals (lead, cadmium,
zinc, nickel, manganese).
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SOIL PROPERTIES AND FERTILITY
- Weathering of soil parent materials
(inorganic minerals) and biodegradation of
organic matter results in available soil
nutrients. The atmosphere provides all others
(C, H, O).
- Soil physical and chemical properties
determine the availability of various plant
nutrients. 1. Clay type and amount Affects
nutrient holding capacities (cation exchange
capacity) high in clay soils low in sandy
soils
2. pH 3. Organic matter
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Nutrient availability, more than absolute
quantity, determines plant nutrient status
The most nutrients are Generally available
between pH 6.0-7.0
pH
Fig. 5.4. Effect of soil pH on the availability
of mineral nutrients. At low pH levels, toxic
amount of Fe, Mn, and AI may be present, but P
is unavailable due to conversion to insoluble
phosphates with Fe and AI. At high pH levels, P
reacts with Ca and becomes insoluble. (Courtesy
of University of Kentucky Extension Service)
Ca, Mo - higher availability _at_ higher pH Zn,
Fe, Mn, Al - higher availability _at_ lower pH Fe,
Mn, Al may be toxic in very acid soils
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PLANT NUTRITION
Nutritional Status of Plants 1. Deficient 2.
Transitional 3. Adequate 4. Toxic
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PLANT NUTRITION
Critical concentration Lowest tissue
concentration at which optimal growth
occurs. Critical tissue levels have been
determined for numerous crops. Deficiency
zone element dry matter Adequate
zone element tissue
concentration (no change in
DM) Toxic zone element
dry matter
Luxury consumption additional uptake
without Additional plant growth.
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TISSUE TESTING

• Difficulties with fertilization based on tissue
  testing
• Deficiency is already present before it
• can be detected.
• 2. Sampling procedures (leaf number, age) must
  be standardized.
• 3. Environmental effects (short-term anomalies)
  may affect results.
• 4. Genetic (cultivar, variety) differences.
• 5. May not be related to amount of nutrients in
  soil, but may indicate availability only.

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CROP FERTILIZATION
Fertilization of a crop must be based on 1)
Amount of nutrients needed 2) Cost per unit of
nutrient 3) Yield increase expected from
addition of nutrient
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LAW OF DIMINISHING RETURN
LAW OF DIMINISHING RETURN Each added fertilizer
increment produces a progressively smaller yield
increase.
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NUTRIENT UPTAKE
A physical or chemical proximity to the root
is necessary for nutrient uptake. Contact can be
made by 1. Contact exchange 2. Exchange of
soil ions with H in the mucigel 3. Diffusion
in response to chemical gradient 4. Mass flow
in response to moisture gradient 5. Extension
of root to ion
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• Contact exchange
• Exchange with soil solution
• Diffusion
• Mass flow
• Roof extension

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NUTRIENT ABSORPTION
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Symplasm inside cells (dotted
areas) Apoplast outside cells (clear areas)
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ENDODERMIS
ENDODERMIS Barrier to passive movement via the
apoplast because of casparian strip (which is a
barrier to passive movement). Movement through
the endodermis is thought to be by active
transport.
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ION MOVEMENT ACROSS MEMBRANES
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FUNCTION AND USE OF NUTRIENTS
I. Basic structure II. Energy storage and
transfer III. Charge balance IV. Enzyme
activation
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FUNCTION OF NUTRIENTS
I. STRUCTURE
C H O
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FUNCTION OF NUTRIENTS
II . Energy Storage and Transfer Nitrogen -
NO3-, NH4 (nitrate, ammonium) amino acids,
proteins, nucleic acids Sulfur - SO4- -
(sulfate) amino acids, proteins,
enzyme activation Phosphorous - H2 PO4- -
(orthophosphate) ATP, ADP, NADPH, DNA,
RNA, Membranes
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FUNCTION OF NUTRIENTS
III. Charge Balance Potassium - K
(potassium ion) enzyme activator, maintenance of
osmotic potential balance of charges stomatal
opening. Calcium - Ca (calcium
ion) component of cell walls cell division
and elongation meristem function. Magnesium -
Mg (magnesium ion) center of chlorophyll
molecule important in enzymatic reactions

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FUNCTION OF NUTRIENTS
IV. Enzyme activation and electron transport
Fe Mn Zn B (H3BO3 - Boric Acid)
Cu MoO4- - (molybdate) CL-
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N, P, S Energy Storage and Transfer K, Ca, Mg
Charge Balance Fe, Mn, B, Cu, Zn, Mo, Cl
Enzyme Activation Electron Transport