Transport
In Plants
Water Potential
•  The physical property
predicting the direction in
which water will flow
– ____________________
– 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
•  _____________:
accumulation of
water
Transport of Xylem Sap
•  ______________
– Transpiration
• evaporative loss of H2O from a
plant through the stomata
Transport of
Xylem Sap
The Control of
Transpiration
•  ______________
– 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
• ____________– 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
_______________
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
– _______ – 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
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
•  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
•  _____________ 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
• 
• 
• 
• 
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
•  ____________
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
_________
(an amino
acid similar
to arginine)
•  Recruitment
of predatory
animals
Why plants are
important?
•  Food!
•  Humans have domesticated plants for
13,000 years.
•  ____ 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
• _____ of all US
Prescription Drugs
contain one or more
active ingredients from
plants.
• ____ 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
__________
•  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.
•  From _____________ 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