Diffusion, Osmosis, and Active Transport
Short-Distance Intercellular Transport
The Water Available in Water
Long-Distance Transport: Xylem
Water Potential
Long-Distance Transport: Phloem
The Water Available in Air
Transfer Cells
Motor Cells
Guard Cells
Material transferred from cell to cell across membrane
apoplast
symplast
Active Transport
cells interconnected by plasmodesmata
Diffusion
diff regions get diff amounts water
air pulls water out of plants
variety of forms
air supplies water to land plants
timing & regularity of precipitation important
eutrophication
water starts out as rain
ocean water
sources
sinks
water at top mountains pure
Water Transport Through Xylem
Properties of Water
pressure flow hypothesis
Control of Water Transport by Guard Cells
three components
free energy of water
Cells and Water Movement
water moves from positive to negative regions
measured in megapascals
pressure
similar to guard cells
plasma membrane
larger membrane
found in areas w/rapid short-distance transport
examples
move slowly and reorient themselves
desert none/little precipitation
fog & cloud regions
night
day
osmosis
molecular pumps
small molecules move through wall and intercellular spaces
glandular regions
fusion between transport vesicles & plasma membrane
all of the protoplasm of one plant
nonglandular regions
one continuous mass
algae die
fresh
molecular pumps
examples
motive force for transpiration
fine cytoplasmic channels
less pure as it collects
too much salt
salty
particles move high to low
brackish
frost
very pure
rain
snow
through a membranne
dew
sugars actively unloaded from sieve elements into surrounding cells
fog
hail
humidity
receive transported phloem sap
pressure potential
not all active simultaneously
rate water lost
movement influenced by powered by water loss in atmosphere
osmotic potential
pressure potential
water heavy
little internal pressure
guard cells close
shrunken
active transport
membrane bound molecular pumps
osmotic potential
bodies decomposed by bacteria
uses up so much oxygen
can't grow w/out phosphate
mostly cell wall :
mc absorbed
sugars actively transported
sites where nutrients are transported
intercellular space
extremely diverse
phloem loading
respiration
protein
proton pumping photosynthesis
cohesion tension hypothesis
cavitation
water loss through cuticle
most powerful mechanism
MPa
heavy
cells grow not burst
use ATP to force molecules across membrane
matric potential
moves when diff in water potential in cell
decreased
bars
negative
algae can't live here
finger-like/ ridge-like outgrowths inner surface
light most often controls guard cells water relations
potentials always in pairs/groups
water always in air
positive
can accumulate or expel K+
capacity to do work decreased
location of flexture
movement based on simple properties & solutions
osmotic potential less neg
Prayer Plant
guard cells open
more molecular pumps
pressed firmly against all convolutions
water potential less neg
plants don't all produce organs @ same time
change enormously
flex and fold in response to stimulus
distelled
increased
equal in two regions
cannot use to hydrate
tension on mc (pull)
effect of pressure on water potential
intracellular transport
process reversed
outer surface area of walls smooth
hydrophobic molecules
pass through primary cell walls
fruits can only develop after flowers
hydrophyilic molecules
sieve elements
storage sites
Venus Flytrap
ATP splits into ADP & phosphate
kills fish
effect solutes have on water potential
open stomatal pores allow water loss
water mc must lift weight of entire water column
Osmosis
breaks hydrogen bonds
sieve cells
other plants
hydraulic equilibrium w/surrounding cells
exception in CAM plants
triggered by water stress
along numerous vascular bundles
does not increase or decrease more than a few megapascals
loss of sugar
phloem sap more dilute
sigh pie
water loss still problem
leaves dehydrate
= 10 bars
lifting to top of tree requires a lot of energy
often occurs in early afternoon
leaves dominant
cool
adjust water potential & turgidity
number of particles present in solution
mc move easily
pressure potential neg #
tracheid or vessel can never conduct water again
where petiole attaches to lamina or stem
water molecules interact w/ other substances
K+ ions actively transported
blue light
early spring
water molecules interact strongly w/one another
lowering it
something compressed
entire midrib
decrease pressure
K+ pumped from guard cells -> surrounding cells
membrane extremely impermeable
energy transported to pump
water under pressure decreases
something stretched
much larger surface area than flat
adheres to substance
heat
diffuse easily through any membrane
elevation
sugar accumulation causes concentration
equalibrium
binds to molecule & ATP
no net movement of water
increase pressure
pure water
photosynthetic fixing of CO2
polar
plants other than angiosperms
water diffuses outward
phloem loaded by polymer trap mechanism
water under pressure increases
significant when stomatal pores open
adding soultes
transstomatal transpiration
apoplastic space
completely impermeable
doesn't break cells
incipient plasmolysis
vesicles migrate through cytoplasm and fuse with organelle
freely permeable
release abscisic acid
pressure builds
no net change occurs
differentially permeable membranes
inner bark in storage roots & stems
network bundles in tublers & corms
cohesion overcome
massive loading
warm, dry days
spring
summer
water's adhesion to dissolved structures
K+ cannot leave once inside
diffusion not possible
guard cells close stomatal pore
fine veins in leaves
surrounding cells -> guard cells
water enters & leaves same rate
differentially/selectively permeable
adhesive
cells @ joints
cohesive
triggerswavelength
STM/CC complex
membranes permeable to mono & disaccharides
simple sugars diffuse into conducting cells
hydraulic disequalibrium
water follows
equilibrium
open means trade off
osmotic potential more neg
water potential more neg
water potetial decreasses
hydrophobic
epidermal & mesophyll cells lose water
palisade parenchyma
some water lost through cuticle
filled w/ moisture saturated air
spongy mesophyll
decrease in internal carbon may lead to openings
vesicle contents transferred
pressure potential decreases
only if has aqauporins
isolation barriers
no solutes
water potential increases
all solutes
impermeable plasma membrane
not reached equilibrium
decreases water free energy
nothing passes through
little biological significance
quite important
protoplast loses just enough water to pull slightly from walls
mass transfer
large volume of material flows from source
membranes merge
pressure potential increases
water column breaks
end cells do not swell
soil particles
phloem sap flow rapidly into sink
only decreases water's free energy
only certain substances
hydrogen bonding broken
water adheres firmly to soil particles
almost all substances
hormone
cell walls
membranes
lipid/protein membrane
lipids don't interact w/water
polymerized into polysaccharides
potentials more neg
transcuticular transpiration
protoplasm squeezed
CO2 absorption
presure builds,
H2O water loss
little water passes through
protoplast pulls away completely & shrinks
osmotic potential negative
nutrients/sugars transported by phloem per hour
dry soil
specific mass transfer
phloem sap under pressure
matric potential always negative
acts as broken cable
membrane disintegrates
water not absorbed easily
danger uncontrolled bleeding
mc above cavitation point
osmotic potential 0.0MPa
vacuolar creates phloem sap
two mechanisms seal sieve elements
drawn rapidly upward
P-protein
callose
free of water weight below them
fine network
pressure drop
not in conifers
in all eudicots
stays in solution only under pressure
phloem ruptured, P-protein swept in cell center
protein channels
if cut
advantageous in wet soil
mc below cavitation point
not in all monocots
adjacent to plasma membrane of uninjured sieve elements
moist soil
between points
cell plasmolyzed
tangled mess
callose precipitates into floccurent mass
to large to pass through
embolism
roots absorb free liquid H2O
water carries mineral from roots to shoots
rush downward
forms P-protein plug
carried w/P-protein to sieve areas
callose contributes to plug
air bubble
expands till surface encounters solid barrier
transpiration occurs
leaking prevented
no support
pit membrane
prevent heat stress
if dry, potential lethal threat