Plant Mineral Nutrition
Main driving forces for
water flow from the
soil through the plant to the
atmosphere
• Differences in water vapor
concentration,
• Hydrostatic pressure,
• Water potential .
Root hairs
make
intimate
contact
with soil
particles
WATER ABSORPTION BY
ROOTS
Animation
Mineral Nutrients
MINERAL NUTRIENTS ARE ELEMENTS
acquired primarily in the form of inorganic ions from the soil.
The study of how plants obtain and use mineral nutrients is
called mineral nutrition.
Mineral Nutrition
Growth Factors:
What do plants need to grow?
1.
2.
3.
4.
5.
6.
What is an essential plant nutrient?
The criteria for essentiality: Arnon and Stout, 1939
All the nutrients needed to carry out growth and
reproductive success; full life cycle
2. The element cannot be replaced or substituted
1. Omission of the element will result in abnormal growth
3. The element must exert its effect directly on growth
What is an essential plant nutrient?
There are 17 known (accepted) elements that are
essential for plant growth
Hydrogen, Oxygen, Carbon – plant gets from air
and water
The other 14 are mineralized elements derived from
soil (or air as in N)
Other nutrients being studied:
Silicon, Cobalt, Aluminum
Types of Nutrients • 1. The first group of essential elements forms the organic (carbon)
compounds of the plant. Plants assimilate these nutrients via
biochemical reactions involving oxidation and reduction.
• 2. The second group is important in energy storage reactions or in
maintaining structural integrity.
• 3. The third group is present in plant tissue as either free ions or
ions bound to substances such as the pectic acids present in the
plant cell wall.
• 4. The fourth group has important roles in reactions involving
electron transfer.
Relationship between plant growth
and nutrient concentration
• What happens when a nutrient or nutrients
are inadequate in supply?
• Can the concentration of a nutrient be too
high?
Plant growth progresses to
the limit imposed by the
nutrient in least supply
What is an essential plant nutrient?
Techniques Are Used in Nutritional Studies
Absence or excess of any
nutrient….. Hoagland
solution
1)Hydroponics
2) Nutrient film growth
system
3) Aeroponic growth system
Mineral Deficiencies Disrupt Plant Metabolism
and Function
• Both chronic and acute deficiencies of several
elements may occur simultaneously.
• Deficiencies or excessive amounts of one element
may induce deficiencies or excessive accumulations
of another.
• Some virus-induced plant diseases may produce
symptoms similar to those of nutrient deficiencies.
Forms in which nutrients exist
• cation – positively charged ion
• anion – negatively charged ion
• neutral – uncharged
• Plants used the mineralized from of a nutrient – It does not matter to the plant where it comes from
So which nutrients exist in what form?
• ammonium – NH4+
• potassium – K+
• calcium – Ca+2
• magnesium – Mg+2
• iron – Fe+2, Fe+3
• zinc - Zn+2
• manganese Mn+2, Mn+4
• copper – Cu+2
• cobalt – Co+2
• nickel – Ni +2
• nitrate – NO3-
• phosphate – H2PO4- , HPO4
-2
• sulfate - SO4-2
• chlorine – Cl-
• borate - H3BO3, H2BO3-, B4O7
-2
• molybdate – MoO4-2
Anions Cations
Factors that affect nutrient uptake
• Getting nutrients to the plant roots
– Nutrients are water soluble
• What factors affect nutrient availability
– pH
– Cation Exchange Capacity
• Colloids (humus, clay)
Getting nutrients to the roots: Mechanisms for nutrient delivery
• mass flow
– the passive movement of nutrients in soil water
to roots
• diffusion
– the movement of nutrient from regions of high
concentration to regions of low concentration
• root interception
– direct contact of nutrients with roots as roots
grow and explore soil
Getting nutrient to the roots:
Mechanisms for nutrient
delivery
Properties Affecting Nutrient Availability
p = potential or power
H = hydrogen
Chemical Properties - pH
• pH and hydrogen ion
concentration are inversely
related.
• As pH increases, hydrogen
ion concentration
decreases.
Chemical Properties - pH
• Logarithmic scale
pH of 6
has 10x more H+
than pH 7
pH [H+] [H+]
1 10-1 .1
2 10-2 .01
3 10-3 .001
4 10-4 .0001
5 10-5 .00001
6 10-6 .000001
7 10-7 .0000001
8 10-8 .00000001
9 10-9 .000000001
Properties Affecting Nutrient Availability
Chemical Properties - pH
pH affects the availability of nutrients
Properties Affecting Nutrient Availability
Chemical Properties – Cation Exchange Capacity C E C
• ammonium – NH4+
• potassium – K+
• calcium – Ca+2
• magnesium – Mg+2
• iron – Fe+2, Fe+3
• zinc - Zn+2
• manganese Mn+2, Mn+4
• copper – Cu+2
• cobalt – Co+2
• nickel – Ni+2
• nitrate – NO3-
• phosphate – H2PO4-HPO4
-2
• sulfate - SO4-2
• chlorine – Cl-
• borate - H3BO3, H2BO3-, B4O7
-2
• molybdate – MoO4-2
Cations Anions
Properties Affecting Nutrient Availability
Growing Media - Chemical Properties
Chemical Properties - pH
OH-
OH-
OH-
OH-
H+ H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+ H+
H+ H+
H+
H+
H+
H+
H+ H+
H+
H+
H+
H+ H+
H+
OH-
pH affects the availability of nutrients
Negatively charged chemical groups OH- on humic particles
Sometimes associated with Fe and Al in clays
pH
High or Low ?
Low
Growing Media - Chemical Properties
pH affects the availability of nutrients
Chemical Properties - pH
H+
H+
H+
H+ H+
H+
H+
OH-
OH-
OH-
OH-
OH-
Negatively charged chemical groups OH- on humic particles
Sometimes associated with Fe and Al in clays
pH
High or Low ?
High
Chemical Properties – Cation Exchange Capacity C E C
The ability of a soil or substrate to provide a nutrient reserve
It is all the exchangeable cations the soil or substrate can adsorb
The CEC of a soil depends on colloids and pH
Properties Affecting Nutrient Availability
The higher the CEC of a soil the better buffering capacity
attracts
Chemical Properties – Colloids and CEC
Colloids - very small particles in soil that are
chemically reactive (charged) – humus, clay
K+ Fe++
Mg++
Mn++
H+
Fe++
Mg++
Mg++
Mn++
H+
H+
Ca++
K+
+
Properties Affecting Nutrient Availability
Growing Media - Chemical Properties
pH affects the availability of nutrients
Chemical Properties - Colloids and CEC
OH-
OH-
OH-
OH-
OH-
Example of one scneario:
some nutrients become more available at low pH
Mn++
Mn++
Mg++
Mn++
Mn++ Mg++
Ca++
Fe++
Fe++
Fe++
Fe++
Fe++
Growing Media - Chemical Properties
pH affects the availability of nutrients
Chemical Properties – CEC
OH-
OH-
OH-
OH-
OH-
H+ ions vie for space, certain ions released becoming available
Mn++
Mn++
Mn++
Mn++
Mn++
Mn++
Ca++
Fe++
Fe++
Ca++
Fe++
Fe++
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+ H+
H+ H+
H+
H+ H+
H+
H+
H+
H+
H+
pH ≈ 5.8
Chemical Properties – Cation Exchange Capacity C E C
The ability of a soil or substrate to provide a nutrient reserve
Types of Soil Colloids Cation Exchange Capacity
(cmolc/kg of colloid)
humus 100-300
vermiculite 120-150
montmorillonite 60-120
illite 15-40
0-3* iron oxides
Properties Affecting Nutrient Availability
10 – 10 – 10
What’s on the Bag
N P K
# - # - #
N
1.00
N
0.44 0.83 –
–
–
– P K
– P2O5 – K2O
The Major Players – N and P
• Nitrogen
– NO3- N and NH4
+-N or urea
• Phosphorus
– H2PO4--P at pH of 5.0 to 6.5
Nitrogen (N)
– NO3- N and NH4
+-N or urea
utilized for a variety of structural and metabolic compounds
over half of N in plants is found in the leaves of plants
between 15 and 30% of that leaf nitrogen goes into the production
of Ribulose 1-5-biphosphate carboxylase or Rubisco
Nitrogen is very mobile within the plant
NO3- nitrate
Nitrogen (N)
taken up by plants passively and actively
uptake increases pH in soil
best uptake pH range between 4.5 and 6
nitrate can be stored in plant
nitrates leach
taken up by plants passively and actively
decreases pH in soil
ammonium (ammonia) cannot be stored
must be assimilated immediately by carbon
NH4+ ammonium
ericaceous species utilize
Nitrogen (N)
Phosphorus (P)
H2PO4- -P at pH of 5.0 to 6.5
High pH, P binds with calcium
Low pH P, binds with iron
High P fertilizers do not promote root growth
Utilized for energy transfer, membrane structure, nucleic acids,
proteins
Mobile in plant
Nutrient Interactions: Relationships of elemental excess
in growing media to potential nutrient deficiencies in plant tissue.
Element in excess in media Element possibly deficient in plant tissue
Nitrogen as ammonium Potassium, Calcium, Magnesium
Potassium Nitrogen, Calcium, Magnesium
Phosphorus Copper, Zinc, Iron
Calcium Magnesium, Boron
Magnesium Calcium, Potassium
Sodium Potassium, Calcium, Magnesium
Manganese Iron, Molybdenum
Iron Manganese
Zinc Manganese, Iron
Copper Manganese, Iron, Molybdenum
Molybdenum Copper
Aluminum: this element is not essential and high levels are rare in artificial soils. High Aluminum will precipitate Phosphorus as Aluminum Phosphate and can highly reduce short term Phosphorus availability.
Mobility of Plant Nutrients: Mobility of elements in the
plant often defines the location of visual symptoms of nutrient deficiencies or toxicities:
Very Mobile
Moderately Mobile
Limited Mobility
Nitrogen Magnesium Iron
Phosphorus Sulfur Manganese
Potassium Molybdenum Copper
Chlorine Zinc
Calcium
Boron
* Most recently matured leaves are the most accurate leaf sample for nutrient analysis.
Nutrient Form:
Organic or Inorganic?
• Plants used the mineralized form of a nutrient
– It does not matter to the plant where the nutrient comes from,
as all nutrients taken up are in a mineralized form
– See handout on types of organic and inorganic fertilizers
• However adding composted organic matter to your soil
will aid in nutrient availability
– See lesson on soils
Nutrient Form:
Composts and Teas?
• Composts are denatured organic materials
– A true aerobic compost requires 3 things
• Aeration
• Moisture – 40 to 60 %
• A C:N ratio of 30 to 1
• Anaerobic composting – less heat, more break down,
increased humus production, but more noxious gases
• Making teas from composts is easy, however
making a consistent product is not
– Anti-pathogen properties
Foliar Nutrient Application
• Plants use the mineralized form of a nutrient – The majority of nutrient uptake are via plant roots
– Nutrients can be applied via foliar application
– Foliar application should merely be supplemental
• For most nutrients
– If foliar application is the primary method of nutrition
something is wrong with your soil ! (or roots)
Other Negative Effects of Nutrient Over-application
• Runoff
• Physiological responses
may affect root growth
e.g. recent evidence shows P does not promote root growth
may affect flowering
e.g. over application of N and other nutrients may
stimulate vegetative growth as in grapes
• Inappropriate fertilizers
NO3 is not well utilized by ericaceous species
• Balance your NO3 with your NH4
good for most plants
Timing of Fertility
• Evidence of periodicity in nutrient uptake in some species
• evidence for opposite shoot growth/root uptake periods
• fall uptake for spring growth
• Arborist stress fall fertilization of trees and shrubs
• Some concern over cold hardiness issues with fall N fertility
• Lawn care specialists suggest fall fertilization
• Tree nursery recommendations stress split fertilization
early spring and mid summer
Nitrogen (N)
Deficiency
- occurs in oldest leaves first
- stunted growth yellowing, chlorosis, stunted growth,
leaf drop, increased root shoot ratio
Symptoms of Deficiency and Toxicity
Toxicity
- occurs with ammonium only
- yellowing, chlorosis, root death
- interactions with K, Ca, Mg
Phosphorus (P)
Deficiency
- occurs in oldest leaves first
- older leaves darken and turn purple, leaf margin necrosis,
low production of flowers, fruit and seed
Symptoms of Deficiency and Toxicity
Toxicity
- mostly interactions with other nutrients including
zinc, copper and iron
Potassium (K)
K+
Like phosphorus, potassium exists as many forms in soils, and
much of it is unavailable to plants,
Plants take up potassium in large amounts compared to other
nutrients. Only the demand for nitrogen is greater. In plant
tissue the N:K ratio is close to 1:1.
Maintains a variety of plant metabolic activity mainly by
regulating water status and stomatal control.
Aides in carbohydrate transport and cellulose production.
Mobile in plant
Potassium (K)
Deficiency
- occurs in oldest leaves first
- yellowing of margins and tips of leaves
- edge “scorch”
Symptoms of Deficiency and Toxicity
Toxicity
- mostly interactions with other nutrients including
calcium and magnesium
Sulfer (S)
SO4-2
In soil, the majority of sulfur is found in organic form and to a
lesser extent mineral form as sulfates
Plant roots actively take up sulfur primarily as sulfates SO4 -2,
Plants utilize sulfur in amino acids, proteins, vitamins and other
plant compounds like glycoside oils that give onions and mustards
their characteristic flavors..
Sulfur also activates certain enzyme systems
Not Mobile in plant
Sulfur (S)
Deficiency
- occurs in youngest leaves first
- similar to N deficiency
Symptoms of Deficiency and Toxicity
Toxicity
- There are rarely issues of toxicity
Calcium (Ca)
Ca 2+
Free calcium is loosely bound to organic and mineral colloids
Calcium is taken up passively in roots tips and moves
through the plant primarily via the xylem during
evapotranspiration
Mainly found in the cell walls
Not Mobile in plant
Responsible for membrane stability and cell wall integrity
Calcium is required for the extension of cell walls during cell
growth at shoot and root tips and enhances pollen tube growth.
Calcium (Ca)
Deficiency
- Occurs in youngest leaves first
- Reduction of growth at meristems
- Deformed and chlorotic leaves
- leag margin necrosis
Symptoms of Deficiency and Toxicity
Toxicity
- mostly interactions with other nutrients including
magnesium, potassium causing deficiencies
Mg 2+
Magnesium is made available to the plant through exchange
with soil colloid complexes
Plants take-up magnesium passively, transported mainly through
the phloem
Fifteen to twenty percent of the magnesium in plants is found in
the pigment molecule, chlorophyll.
Mobile in plant
Cofactor for enzymes that help transfer energy and CO2 fixation
Magnesium (Mg)
Assists in RNA translation for protein synthesis
Magnesium (Mg)
Deficiency
- Deficiency symptoms appear in older leaves as interveinal
chlorosis.
Symptoms of Deficiency and Toxicity
Toxicity
- There is typically no magnesium toxicity.
Cl -
Chlorine naturally occurs in soils as constituents of many soil
minerals and is made available through natural weathering.
Taken actively and passively depending on soil concentrations,
active when low and passive when concentrations are high
Utilized in several processes of photosynthesis.
Mobile in plant
Chlorine (Cl)
Chlorine (Cl)
Deficiency
- Deficiencies are uncommon
Symptoms of Deficiency and Toxicity
Toxicity
Yellowing and burning of leaf tips, with interveinal areas
being bleached, scorched and necrotic in severe cases.
Fe 2+
Iron is ubiquitous in many soils, yet availability depends on
soil chemistry.
Actively taken up by the plant and is transported by xylem
to the leaves.
Utilized in several processes of photosynthesis.
Not mobile in plant
Iron (Fe)
Deficiency
- Iron deficiency is similar to magnesium deficiency
symptoms (interveinal chlorosis), but occurs on youngest
leaves first
Symptoms of Deficiency and Toxicity
Toxicity
- iron interferes with manganese uptake manganese
deficiency (mottled yellowing between veins developing
as necrotic lesions later), as.
Iron (Fe)
Mn 2+
Availability depends on pH and organic colloid content.
Increased in low pH
In the plant manganese is transported in the xylem and delivered
to mertistematic tissue where it is largely immobilized.
Cofactor for many metabolic enzymes and is important factor
in photosynthesis. Used to split water.
Not mobile in plant
Manganese (Mn)
Deficiency
- Interveinal chlorosis, similar to iron and zinc.
Symptoms of Deficiency and Toxicity
Toxicity
- Toxicity varies among species.
- Occurs in acid soil conditions when manganese is most
available
- Dark purple or brown spots within the leaf margins and/or
leaf tip necrosis
- Toxicity varies among species. Plants associated with acid
soils are naturally tolerant to high manganese conc.
- Severe toxicity results in stunted and yellowed meristems.
Manganese (Mn)
H3BO3
Availability depends on pH and organic colloid content.
Increased in low pH
Boron moves into the plant, passively taken up in solution by the
roots via evapotranspiration, moving through xylem
Factor in cell growth, including division, differentiation, and
elongation
Not mobile in plant
Boron (B)
Cell processes like carbohydrate metabolism and other
metabolic pathways
Concentrated at growth areas including reproductive structures.
Deficiency
- Since boron is associated with cell growth, deficiencies
usually show up in new growth as wrinkled and withered
leaves, with tip death soon after.
- Like calcium, deficiencies may be caused by drought or
high humidity.
Symptoms of Deficiency and Toxicity
Toxicity
- Toxicity can develop quickly, the range between deficient
and toxic supply is small.
- Different tolerances among plant species.
- Yellowing of the leaf tips, interveinal chlorosis and leaf
margin scorching.
Boron (B)
Cu 2+
Optimally available in slightly acid conditions where the copper
ion exchanges with other cations on soil colloids
Root uptake is active and copper moves in the xylem, complexed
with amino acids and other nitrogenous compounds.
Copper is utilized with enzymes for metabolic activities and
photosynthesis.
Not mobile in plant
Copper (Cu)
Deficiency
- Deficiencies of copper show up on the youngest leaves
first
- Depressed and twisted growth
- New leaves appear pale along the margins but green at the
end of the veins.
- Spotty necrosis occurs in the leaf margins. Stems may
become distorted and twisted.
Symptoms of Deficiency and Toxicity
Toxicity
- Toxic levels of cooper induce iron deficiency and
accompanying symptoms along with depressed root
growth.
Copper (Cu)
MoO4 -2
Molydenum uptake is dependent on solubility of the ion. Unlike
many micronutrients, molybdenum becomes more available in
higher pH.
In the leaf, used for an important enzymatic process called nitrate
reduction, the first of two important physiological steps that
make nitrate usable in the plant
Relatively mobile in plant
Molybdenum (Mo)
Deficiency
- Since molybdenum is essential for nitrate reduction, a
deficiency in molybdenum manifests as a nitrogen
deficiency
- leaf chlorosis in older leaves
- then leaf margin wilting
- leaf and meristem death
Symptoms of Deficiency and Toxicity
Toxicity
- rare in soils and plants can tolerate relatively high levels of
molybdenum
Molybdenum (Mo)
Zn +2
Slightly mobile in plant, mainly stored in roots
Zinc (Zn)
present in sulfide and silicate minerals and is also associated
with organic colloids
Zinc is actively taken up by plants and transported through the
xylem metabolic functions including auxin (growth hormone)
production, a cofactor in protein synthesis, enzyme activity and
carbohydrate metabolism and regulation.
chlorophyll production
may enable plants to tolerate colder temperatures
Deficiency
- Symptoms on older leaves first
- Include interveinal chlorosis, curled and dwarfed leaves
and then leaf scorch and necrosis.
- excessive phosphorus can interfere with zinc uptake
Symptoms of Deficiency and Toxicity
Toxicity
- May occur in low pH soils (< pH 5) or where municipal
sludge has been added to soils
- Toxicity concentrations are species dependent
- interfere with iron uptake
Zinc (Zn)
Ni +2
Possibly mobile in plants
Nickel (Ni)
Nickel is the newest recognized essential plant nutrient
requirement was not known because impurities in
irrigation water and fertilizers supplied the very low
requirements of this nutrient
required for the enzyme urease to metabolize urea, releasing
the ammoniacal nitrogen for plant use
for iron absorption and seeds production and germination
evidence to suggest that carbon respiration and nitrogen
metabolism are sensitive to Ni nutrition
Deficiency
- rounded, blunt and slightly curled leaves known as
“mouse-ear”
- seen on spring growth and is a result of accumulation of
urea to the point of toxicity
Symptoms of Deficiency and Toxicity
Toxicity
- At a level of 100 ppm or higher, nickel is considered to be
phytotoxic
- toxicities typically exist in areas where industrial waste has
been concentrate
- In beets severely stunted growth; young leaves at early
stage show chlorotic iron deficiency symptoms, followed
by severe necrosis, collapse and death
Nickel (Ni)
Analysis of Plant Tissues Reveals
Mineral Deficiencies
• Soil analysis vs plant tissue analysis
Add new methods?
TREATING NUTRITIONAL
DEFICIENCIES • Crop Yields Can Be Improved by addition of
Fertilizers
• Soil pH Affects Nutrient Availability, Soil
Microbes, and Root Growth
• Different Areas of the Root Absorb Different
Mineral Ions
• Mycorrhizal Fungi Facilitate Nutrient uptake
by Roots
• Excess Minerals in the Soil Limit Plant
Growth
Discussion Paper
• For Next WEEK
Plant Cell Physiol. 2014 Dec;55(12):2027-36. doi: 10.1093/pcp/pcu156. Epub 2014 Nov 6.
Strategies for optimization of mineral nutrient transport in plants:
multilevel regulation of nutrient-dependent dynamics of root
architecture and transporter activity. Aibara I1, Miwa K2.
Abstract
How do sessile plants cope with irregularities in soil nutrient availability? The uptake of essential
minerals from the soil influences plant growth and development. However, most environments do
not provide sufficient nutrients; rather nutrient distribution in the soil can be uneven and change
temporally according to environmental factors. To maintain mineral nutrient homeostasis in their
tissues, plants have evolved sophisticated systems for coping with spatial and temporal variability
in soil nutrient concentrations. Among these are mechanisms for modulating root system
architecture in response to nutrient availability. This review discusses recent advances in
knowledge of the two important strategies for optimizing nutrient uptake and translocation in
plants: root architecture modification and transporter expression control in response to nutrient
availability. Recent studies have determined (i) nutrient-specific root patterns; (ii) their
physiological consequences; and (iii) the molecular mechanisms underlying these modulation
systems that operate to facilitate efficient nutrient acquisition. Another mechanism employed by
plants in nutrient-heterogeneous soils involves modification of nutrient transport activities in a
nutrient concentration-dependent manner. In recent years, considerable progress has been made
in characterizing the diverse functions of transporters for specific nutrients; it is now clear that
the expression and activities of nutrient transporters are finely regulated in multiple steps at both
the transcriptional and post-transcriptional levels for adaptation to a wide range of nutrient
conditions.
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