Transport
In Plants
Water Potential
• The physical property
predicting the direction in
which water will flow
Solute Concentration
– ____________________
– Pressure
• water moves from high water
potential to low water potential
Water Potential (a)
• Left Side
– Pure Water = 0
Water Potential
• Right Side
– Negative Water
Potential
• 0 pressure
• - solute (has solutes)
• Water moves to the
right
Water Potential (b)
• Left Side
– Pure Water = 0
Water Potential
• Right Side
– 0 Water Potential
• + pressure equal
to solute conc.
• - solute (has
solutes)
• Water is at
equilibrium
Water Potential (c)
• Left Side
– Pure Water = 0
Water Potential
• Right Side
– Positive Water
Potential
• + pressure more
than solute conc.
• - solute (has
solutes)
• Water moves to
the left
Water Potential (d)
• Left Side
– Pure Water and
Negative Tension
• Right Side
– Negative Water
Potential
• 0 pressure
• - solute (has
solutes)
• Water moves to
the left
Transport of Xylem Sap
• Pushing Xylem
– Root Pressure
• caused by active
pumping of
minerals into
xylem
Guttation
• _____________:
accumulation of
water
Transport of Xylem Sap
Xylem
• Pulling
______________
– Transpiration
• evaporative loss of H2O from a
plant through the stomata
Transport of
Xylem Sap
The Control of
Transpiration
Guard Cells
• ______________
– turgid - open
– flaccid - closed
• Potassium Ions
– active transport of H+ out of
cell causes K+ to move in
Stomata
• Open during the day / Closed
at night
– first light (blue light receptor)
– depletion of Carbon Dioxide
– internal clock (circadian rhythms)
Reducing
Transpiration
• Small, thick
leaves
• Thick cuticle
• Stomata are
recessed
• Lose their leaves
• C4 or CAM plants
Translocation
of Phloem Sap
Translocation of Phloem
• Phloem Sap
– 30% sucrose, minerals, amino acids,
hormones
– Transported in sieve-tube members
Sugar source leaves, tuber or bulbs
• ____________–
• Sugar sink – growing roots, shoots,
fruits
Pressure Flow
and
Translocation
A
A) Pressure is high
B) Pressure is low
C) Xylem recycles water
D) Allows Phloem sap to flow
from source to sink
C
B
Plant Nutrition
Uptake of
Nutrients
Hydroponic
_______________
cultures used to
determine which
chemical elements are
essential.
17 essential elements
needed by all plants
Soil
• Develops from weathered
rocks
– Anchors plants
– Provides water
– Provides dissolved minerals
Soil Texture
• Pertains to sizes of soil
particles
– includes the following:
• sands (0.02 - 2 mm)
• silt (0.002 - 0.02 mm)
• clay (less than 0.002 mm)
Soil Composition
• Made up of sand, silt,
clay, rocks, humus,
microorganisms (bacteria,
fungi, algae, protists,
insects, worms, roots)
• Soil contains a mixture of
different sized particles
Loams – roughly equal
– _______
amounts of sand, silt, and
clay – most fertile
The availability of soil
water and minerals
The availability of soil
water and minerals
• Plant takes up water not tied to
hydrophilic soil particles
• Positively charged ions attach to soil
• H+ help displace minerals attached to
soil
• Roots add H+ to the soil directly and
CO2
through the release of ____
• (reacts with water to form carbonic
acid)
The availability of soil
water and minerals
Soil Conservation
• Fertilizers
– (Nitrogen, Phosphorus,
Potassium)
The Nation that Destroys Its Soil Destroys Itself – Franklin D.
Roosevelt 1937
Loss of Topsoil
Black Blizzards
• 1930’s “_____________”
• Due to inappropriate farming in
late 1800’s and early 1900’s
• Wheat and cattle farming
• Droughts
• Steinbeck’s Grapes of Wrath
• 30% of world’s farmlands have
reduced production due to poor
soil conditions.
Nitrogen Fixation
Nitrogen Fixation
• Plants absorb nitrogen in the
form of nitrate
Nitrogen-fixing
• _____________
and
ammonifying bacteria
produce ammonium
• Ammonium is shifted to
nitrate by nitrifying bacteria
• Plants shift nitrate back to
ammonium for use
Nitrogen Fixation
Unusual Nutritional Adaptations in Plants Epiphytes
Unusual Nutritional Adaptations
in Plants - Mistletoe
Unusual Nutritional Adaptations
in Plants – Venus Fly Traps
Unusual Nutritional Adaptations
in Plants – Pitcher Plants
Unusual Nutritional Adaptations
in Plants - Sundews
Control Systems in
Plants
Plant Hormones
• Coordinates growth
• Coordinates development
• Coordinates responses to
environmental stimuli
Plant Hormones
• Auxin (IAA)
• Cytokinins
• Gibberllins
• Abscisic Acid
• Ethylene
• Oligogaccharins
• Brassinosteroids
Auxins
• Stimulates stem elongation
• Stimulates root growth
• Stimulates differentiation and
branching
• Stimulates development of
fruit
• Stimulates apical dominance
• Stimulates phototropism and
gravitropism
Auxin Control
• Auxin stimulates
growth
• Auxin block on
right causes cells
to elongate and
the plant bends
left
• Auxin block on left
causes cells to
elongate the the
plant bends right
•
•
•
•
Acid Growth
___________
Hypothesis
Proton pump stimulated by auxin lower pH of wall
H+ activates Enzyme
Enzyme breaks hydrogen bonds in cellulose
Wall takes up water and elongates
Auxin Others
• Promotes secondary
growth by stimulating
vascular cambium and
secondary xylem
• Promotes adventitious
root at the base of a cut
stem
• Promotes fruit growth
without pollination
(seedless tomatoes)
Cytokinins
• Stimulates root growth
• Stimulates cell division and
differentiation (with auxins)
– more cytokinin - shoot buds
develop
– more auxin - roots develop
• Stimulates germination
• Delays Senescence
Gibberellins
• Promotes seed and bud
germination
• Promotes stem elongation
• Promotes leaf growth
• Stimulates flowering and
fruits
– (with auxin)
Abscisic Acid
• Slows growth
• Closes stomata under water
stress
• Permits seed dormancy
Ethylene
• Promotes fruit ripening
• Controls Abscission (causes
leaf loss)
Plant Movements
• Phototropism
• Gravitropism
Thigmotrophism
• ____________
Plant Movement
• Rapid Leaf
Movement (39.27)
– drop in turgor
pressure within
pulvini
– sent by action
potentials
Plant Movement
• Sleep Movements (39.21)
– cells on opposite sides of pulvinus
control the movement
Daily and Seasonal
Responses
• Circadian Rhythm
• Photoperiodism
– controls flowering (short-day vs.
long-day)
– critical night length
Photoperiodic Control
Flowering
Hormones
• Experiment
indicates the
presence of
some type of
flowering
hormone
Phytochromes
• Function as photoreceptors / red (660nm) to
far red (730nm)
• Activates kinases (regulatory proteins)
Red vs. Far Red Response
Plant Responses to
Environmental Stress
• Water Deficit
• Oxygen Deprivation
• Salt Stress
• Heat Stress
• Cold Stress
• Herbivores
Responses to Herbivores
• Produce
Canavanine
_________
(an amino
acid similar
to arginine)
• Recruitment
of predatory
animals
Why plants are
important?
• Food!
• Humans have domesticated plants for
13,000 years.
80% of all the calories consumed by
• ____
humans come from six crops: Wheat,
Rice, Maize, Potatoes, Cassava, and
Sweet Potatoes.
• Also, we use plants to feed cattle, 5-7kg
to produce 1 kg of beef.
Pyramid of Net
Productivity
Plants remove CO2
25% of all US
•_____
Prescription Drugs
contain one or more
active ingredients from
plants.
50% earth’s species
•____
will become extinct
within the next 100
years (larger than the
Permian or Cretaceous)
•Only 5,000 of 290,000
species have been
studied.
•3-4 species per hour,
27,000 per year!
Cinchona tree
• Bark contains
quinine
__________
• Grows in the
Andes in peru
• Used since the
early 1600’s to
treat malaria
Aspirin
• Acetylsalicylic acid or ASA
• Dates back to 3000 B.C.
• Greek Physician Hippocrates
prescribed it.
trees
• From Willow
_____________
and
other Salicylate-rich plants
(leaves and bark)
• Scientists at Bayer began
investigating acetylsalicylic
acid as a less-irritating
replacement for standard
common salicylate medicines.
By 1899, Bayer named it this
Aspirin