Mineral Nutrients
I. Introduction
A. Definition
B. Evidence
1. Julius Sachs Experiment
Fig 37.7
Julius Sachs 1860’s
C. Plant Mineral Composition
1. Incorporation
a. As is= Some minerals can be used as is:
e.g. K+ ions for guard cell regulation
b. Combined = Some minerals have to be
incorporated into other compounds to be useful:
e.g. Fe+ in the cytochrome complex of the light
reactions
c. Altered = Some mineral compounds have
to be altered to be useful: NO3- must be
converted to NH4+ inside the plant
d. Water
i. 80–85 % of an herbaceous plant is water.
ii. Water supplies most of the hydrogen and some
oxygen incorporated into organic compounds by
photosynthesis.
iii. But > 90% of the water absorbed is lost by
transpiration.
iv. Water’s primary function is to serve as a solvent.
v. Water also is involved in cell elongation and turgor
pressure regulation
2. Dry weight
a. 95% “organic” – C, H, & O from air &
water, assimilated by photosynthesis
b. 5% inorganic minerals
II. Categories
A. Essential Nutrients
Nutrients that are required for a plant to grow from
a seed and to complete its life cycle.
1. Types:
a. Macronutrients
Elements required by plants in relatively large
amounts.
i. Elements
CHOPKNS
ii. Functions
Ca Mg
Category
Form Available
Uses
Carbon
CO2
Organic compounds
Hydrogen
H20
Organic compounds
Oxygen
CO2 (air), O2 (soil)
Organic compounds
Phosphorus
H2PO4-, HPO42-
Nucleic acids, Phospholipids, ATP
Potassium
K+
Water Balance (stomata), Protein Synthesis
Nitrogen
NH4+, NO3-
Proteins, Nucleic acids, Hormones, Chlorophyll
Sulfur
SO42-
Proteins
Calcium
Ca2+
Cell walls & Membranes, Enzyme Activation
Magnesium
Mg2+
Chlorophyll, Enzyme Activation
Information taken from Table 37.1
b. Micronutrients
These elements are required by plants in relatively
small amounts (<0.1% dry mass).
i. Elements
Fe, B, Cl, Mo, Cu, Mn, Ni, & Zn
ii. Functions
Category
Form Available
Uses
Chlorine
Cl-
Required for photosystem II to split water and water balance
Iron
Fe3+ or Fe2+
Component of cytochromes and enzyme activation
Manganese
Mn2+
A.A. formation, enzyme activation, and split water in PS II
Boron
H2BO3-
Cofactor in chlorophyll synthesis, involved in carbohydrate
transport and nucleic acid synthesis, and role in cell wall
function
Zinc
Zn2+
Cofactor in chlorophyll synthesis and enzyme activation
Copper
Cu+ or Cu2+
Involved with re-dox and lignin biosynthesis enzymes
Nickel
Ni2+
Cofactor in nitrogen metabolism enzymes
Molybdenum
MoO4-2
Essential for mutualistic relationship with nitrogen fixing
bacteria and cofactor for nitrogen reducing enzymes
Information taken from Table 37.1
III. Mineral Deficiencies
A. Dependent on:
1. the role of the nutrient in the plant
2. its mobility
B. Immobile Nutrients
1. Once they have been incorporated into plant
tissue, they remain (can’t return to phloem).
2. Boron, calcium, and iron
3. Growth = normal until the mineral is depleted
from soil; new growth suffers deficiency and thus
youngest tissues show symptoms first.
WHY?
C. Mobile Nutrients
1. can be translocated by phloem to younger (actively
growing) tissue.
2. Cl, Mg, N, P, K, and S
3. When mineral is depleted, nutrients translocated to
younger tissue.
4. Thus older tissues show deficiency & then die
What is the adaptive value of nutrient mobility?
D. Criteria
1. Not common in natural populations.
Why? Plants have adapted to soil components.
2. Common in crops & ornamentals. Why? Human
selection is for biggest, fastest plants. Need more
nutrients than the soil provides.
Crop growth depletes the soil because no organic
matter is returned.
3. Deficiencies of N, P, and K are the most common.
4. Shortages of micronutrients are less common and
often soil type specific.
5. Overdoses of some micronutrients can be toxic.
E. Symptoms
1. Chlorosis – leaves lack chlorophyll: yellow, brittle,
papery. Typically lack of N or Fe.
2. Necrosis – the death of patches of tissue
3. Purpling – deficiency of N or P, causes
accumulation of purple pigments
4. Stunting – lack of water, N
Soils
I. Soil Formation
A. Forces
II. Soil Horizons
B. Characteristics
A. Names
Fig 37.2
III. Orders
A. Definition
B. Primary
C. Locations
IV. Soil Properties
A. Chemistry
1. Minerals
2. Nitrogen–fixing bacteria
3. Mycorrhizal fungi
4. Water
5. Oxygen (Gases)
B. Composition
1. Chemistry – determines which minerals are
present and available, thus affecting plant community
composition
2. Physical nature – affects porosity, texture,
density of soil, which affects #1
3. Soil organisms – decomposition & mineral
return. Interact with roots to make nutrients available
Nitrogen! The only mineral that the plant can ONLY
get from reactions mediated by soil organisms.
C. Texture
1. Soil is created by weathering of solid rock by: water
freeze/thaw, leaching of acids from organic matter,
carbonic acid from respiration + water.
2. Topsoil is a mixture of weathered rock particles &
humus (decayed organic matter).
3. Texture: sand
silt
clay
Large,
spaces
for water
& air
Small, more
SA for
retaining
water &
minerals
V. Topsoil
A. Characteristics
1. Biotic = Bacteria, fungi, insects, protists,
nematodes, & Earthworms! Create channels for air &
water, secrete mucus that binds soil particles
2. Humus: reservoir of nutrients from decaying
plant & animal material
3. Bacterial metabolism recycles nutrients
B. Nutrient Availability
1. Cations in soil water adhere to clay particles
(negatively charged surface)
2. Anions do not bind; thus they can leach! (NO3,
HPO4, SO4)
3. Cations become available for root uptake by
cation exchange – H+ displaces cations on the soil
particle surface
4. H+ from carbonic acid – formed from water +
CO2 released from root respiration
5. Humus – negatively charged & holds water &
nutrients. Thus very important in the soil!
Fig 37.3
C. Soil pH
1. Low pH (acidic) = high H+ concentration
a. More cations released
b. Too much acid – cations leach…..mineral
deficiency
2. High pH (basic)
a. Not enough H+ for cation release….mineral
deficiency
VI. Soil conservation
A. Factors Affecting
1. Natural systems: decay recycles nutrients
2. Agricultural systems: crops harvested,
depleting soil of nutrients & water
3. Fertilizers: N:P:K
a. Synthetic: plant-available, inorganic ions. Faster
acting.
i. Problem:
ii. leaching, acidifying the soil
b. Organic: slow release by cation exchange, holds
water, thus less leaching
B. Phytoremediation
1. Use of plants to extract toxic metals from soil
2. Benefits: easier to harvest the plants than to
remove topsoil!
VII. NITROGEN
A. Why so important?
1. Air is 80% Nitrogen, but…..
2. Macronutrient that is most often
limiting. Why? Is almost always taken up as anions
(NO3-).
3. What’s it used for?
Proteins (AAs), nucleic acids, chlorophyll production,
and ???
The Nitrogen Cycle
N2
N2 fixation
Denitrification
Uptake
NO3
Organic N
NH4
Leaching
B. Nitrogen Cycle
1. Steps:
a. N fixation – conversion of N2 to NH3
b. Ammonification – conversion of NH3 or
organic N into NH4+
c. Nitrification – conversion of NH4+ to NO3d. N reduction – conversion of NO3- back to
NH4+ within plant.
e. N assimilation – incorporation of NH4+ into
AAs, nucleic acids, lignin, others(?) of the plant
All steps within the soil are mediated by bacteria!!!!
Fig 37.10
a. Nitrogen Fixation Process
This process is catalyzed by the enzyme nitrogenase,
requires energy (ATP), and occurs in three ways:
i. Lightening – converts N in air to inorganic N
that falls in raindrops
ii. Non-symbiotic – certain soil bacteria
iii. Symbiotic with Legumes
Legumes: peas, beans, alfalfa
The legume/bacteria interaction results in the formation of nodules
on roots
Plant – gets ample inorganic N source
Bacteria – gets ample carbon source
Fig 37.12
Fig 37.11
iii. Fixation in Non-legumes
Here in the NW: alder
Azolla (a fern) contains a symbiotic N fixing
Cyanobacteria useful in rice paddies.
Plants with symbiotic N fixers tend to be first colonizers.
Why?
b. Ammonification
i. conversion of NH3 or organic N into NH4+
c. Nitrification
i. Unfortunately NH4+ is a highly desirable resource
for free–living bacteria, oxidizing it to NO3-.
ii. Consequently the predominant form of N available
to roots is NO3-.
d. Nitrate Reduction
i. NO3- must be reduced back to NH4+ in order to be
incorporated into organics.
ii. This process is energetically expensive but
required.
e. Nitrogen Assimilation
i. The actual incorporation of NH4+ into organic
molecules in the plant body.
ii. This process is similar to that of an electron
transport chain.
iii. Reduced N passes through a series of carriers that
function repeatedly but in the long run are unchanged.
iv. Usually occurs within the roots.
2. Loses
a. Leaching – loss of NO3- by soil water
movement
b. Denitrification – conversion of NO3- back
to N2
c. ???
C. Nutritional Adaptations
a. Parasitic plants
i. Extract nutrients from other plants
Ex. Mistletoes on Douglas Fir & Ponderosa pine
Ex. Indian pipe – parasite on trees via mycorrhizae
Fig 37.15
http://www.nofc.forestry.ca/publications/leaflets/mistletoe_e.html
http://cals.arizona.edu/pubs/diseases/az1309/
b. Carnivorous plants
i. Digest animals & insects – why?
Grow in soils lacking an essential nutrient
ii. Motor cells!
iii. Trap insects & secrete digestive juices
Ex. Venus flytrap, pitcher plant, Darlingtonia
Figure 37.16
c. Mycorrhizal relationships
i. Fungus & plant roots
ii. Fungus gets carbos
iii. Plants get greater SA for water & phosphorus
uptake
iv. Almost all plant species!
v. 2 types:
Ectomycorrhizae – hyphae form dense sheath over
root; extend into cortex & out into soil. Thickened
roots of woody plants
Endomycorrhize – microscopic, more common.
Fig 37.13
Learning power will
supplant physical power.