Please enable JavaScript.
Coggle requires JavaScript to display documents.
Ch.13 Soils and Mineral Nutrition (Soil and Mineral Availability (Cation…
Ch.13 Soils and Mineral Nutrition
Mineral Deficiency Diseases
Causes
scarcity of minerals
not common in natural populations
low connentration of essential elements
unable to thrive
ex: serpentine soil
extremely deficient in calcium
common in nonnative plants
especially if undergone human artificail selection
require lots of nitrogen and nutrients
excess of minerals
very rare
ex: desert soils
toxicity
aluminium toxicity in acid soils
limit crop production
tropical areas
mine tailings
high levels heavy metals
Symptoms
chlorosis
leaves lack chlorophyll
yellowish
brittle and papery
necrosis
deficiency of nitrogen or phosphorus
accumulation of anthocyanin pigments
dark color or purple hue
death of patches of tissue
location depends on particular element
leaf tips and margins die
potassium deficiency
leaf tissues between veins
manganese deficiency
can be caused by bacterial, viral, or fungal infections
Motile and Immobile Elements
immobile elements
calcium, boron, and iron
after incorporated into tissue they stay in place
do not return to phloem
cannot be moved to younger part of plant
growth normal until soil exhausted
newly formed tissues affected
mobile elements
chlorine, nitrogen, phosphorus, potassium, and sulfur
can be translocated to younger tissue
after exhausted of these elements older leaves sacrificed
overall photosynthetic rate increases
Soil and Mineral Availability
Cation Exchange
cations loosely bound to micelle surface due to charge
roots cannot absorb them directly
cations must first be freely dissolved in soil
cation exchange
roots and root hairs transpire
give off CO2
some CO2 reacts with water
forms carbonic acid
H2CO3
breaks down into a proton and bicarbonate ion
dissociate into second proton and carbonate ion
protons positive charge disrupts electrical attraction of cation
cation liberated
diffuse in direction of root
1 more item...
strike another micelle
1 more item...
proton trapped
decaying matter forms negatively charged matrixes
cellulose crystals of cell walls are especially valuable
hold cations liberated
retain essential elements released by decaying protoplasm
in mulch and humus
hold water
greatly improves soil quality
Soil Acidity
soil pH
concentration of free protons in the soil solution
important for cation exchange
also important in the retention of cations during heavy rain
acidity increases, pH lowers
extremely acidic soil
tends to lose cations too rapidly
repetitively poor soil
pH 4.0 to 5.0
highly alkaline soil
pH 9.0 to 10.0
frequent in dry climates
too few protons to allow cation release
concentrations of minerals excessively high
affects chemical form of certain elements
changes solubility
acidic soils
aluminum and manganese become so soluble as to reach toxic levels
alkaline soils
iron and zinc quite insoluble and unavailable to plants
molybdenum more soluble higher pH
many factors affect acidity
chemical nature of original rock
rainfall
most important
high rainfall
vegetation abundant
acids produced by
respiration
excretion
decay
acidic soil
plants that do best
blueberry
fennel
potatoe
azalea
low rainfall
little vegetation
little to no washing out of soil
soil alkalinity increased
concentration of hydroxyl ions increased
NaOH -> Na+ + OH-
alkaline soil
plants that do best
apple
beet
onion
spinach
Endodermis and Selective Absorption
elements enter by crossing plasma membrane
entering symplastic protoplasm phase
selective permeability and presence/absence of molecular pumps control entry of ions and molecules
certain substance excluded
some substances actively transported
diffuse along cell walls and intercellular spaces in apoloplastic phase
prevents uncontrolled apoploplastic diffusion in roots
caspian strips on all radical walls are impermeable to water
Mycorrhizae and the Absorption of Phosphorus
90 % of species form symbiotic association w/ soil fungi
mycorrhiza
permits plants to absorb phosphorus efficiently
most common type vesicular/arbuscular mycorrhizae
fungi filaments penetrate root cortex cells and branch profusely
form tree shaped arbuscule
other filaments swell into balloon like vesicles
fungi collects phosphate from soil and transports to arbuscules
accumulates as granules
disappear as phosphorus transported into root cell protoplasm
arbuscule collapses and root cell returns to normal
derived from weathering
physical
breakdown of rock by physical forces
wind
water movements
temperature changes
produces a variety of soil particle sizes
course sand
largest
2.0 to 0.2 mm
fine sand
0.2 to 0.02 mm
silt
0.02 to 0.002 mm
clay particles
finest
known as micelles
smaller than 0.002 mm
chemical Involves chemical reactions
most important agents are acids produced by decaying bodies
plants
fungi
acids secreted from living organisms
decreases soil particle size
alters soil chemistry
matrix breaks down
positively charged cations are free
Nitrogen Metabolism
Fixation
conversion of N2 gas to nitrate, nitrite, or ammonium
different means
human manufactorin
fertilizer industry
extremely expensive/energy intensive process
natural process
lightning
energy through air converts elemental nitrogen to a useful form
dissolves in rain
falls to earth
fix over 190 million tons of nitrogen annually
nitrogen-fixing bacteria and cyanobacteria
most important
fix over 130 million tons of nitrogen annually
have nitrogenase
enzyme that uses N2 as a substare
forces electrons and protons onto nitrogen, reducing it from +0 to -3
ammonia, NH3 product
immediately dissolves in cell's water and picks up proton
ammounium ion, NH+4
giant enzyme complex
dinitrogenase
four proteins
dinitrogenase reductase
two proteins
molecular weight of 300,00 daltons
cntains numerous atoms of iron, molybdenum, and vanadium
sensitive to oxygen
free living organisms
example
Azotobacter
Clostridium
Klebsiellla
Nostoc
fix nitrogen used in metabolism and becomes available for plants and fungi
only when they die and decay
symbiotic organisms
example
alfalfa
growing inside tissues of host
produce more fixed nitrogen at greater rate than free living
energy resources of plant available
Reduction
process of reducing nitrogen in the nitrate ion from an oxidation of +5 to -3 oxidation state of ammonium
nitrogenase automatically reduces nitrogen during fixation process
if plant can absorb that form then no further reduction necessary
requires eight electrons for each nitrogen atom and a great deal of energy
step 1
nitrate reductase carries electrons by means of a molybdenum atom
nitrate reductase becomes oxidized and picks up more electrons
two electrons added, reducing nitrogen & forming nitrate
step 2
nitrate reductase adds six electrons to nitrate
reducing it to ammonium
ATP not consumed
Assimilation
incorporation of ammonium into organic molecules in the plant body
process is similar to that of an electron transport chain
reduced nitrogen passes through a series of carriers that function repeatedly but in the long run are not changed
acceptor molecule is glutamate
reacts with ammonium and ATP
produces glutamine and ADP
transfers ammonium to alpha ketoglutarate
aka amino group
transforming both molecules into glutamate
extra glutamate produced and can transfer its amino group
if transferred to oxaloacetate then amino acid aspartate is produced
if pyruvate receives amino group then amino acid alanine is produced
transamination
occurs in roots
Other Aspects of Prokaryotes and Nitrogen
some bacteria oxidize nitrogen
nitrifying bacteria
oxidize ammonium to nitrite
oxidize to nitrate
process oxidizing called nitrification
more readily washed from soil cause neg charged and remains in solution
nitrite never build up in soil
Obtaining Nitrogen from Animals
carnivorous plants
mechanisms that trap and digest animals
many bog-adapted plants obtain reduced nitrogen from catching animals
ant-plants
flowering plants and ferns that obtain reduced nitrogen from animals
ex:
Myrmecodia
Hydnophytum
Solanopteris
epiphyletic
roots attached to tree trunks or branches
hollow chambers for dead ants and waste to decompose
domatium
provide living space
mutualistic
Storage of Minerals Within Plants
plants rarely store minerals or nitrogen as crystallized or polymerized forms
all parts of plant except seeds store minerals in soluble form in central vacuoles of cells
nitrogen can be concentrated a little by being converted to compounds w/multiple amino groups
asparagine
citrulline
phosphates, sulfates, and other mineral nutrients are simply sequestered in the central vacuole in the same forms as they are used
does not allow for storage of large amounts
seeds store minerals
lightweight and packed w/enough resources to get established
phytin
myo-inositol-hexaphosphate
six carbon sugar
six hydroxyl groups, each carrying a phosphate bond
