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Transport Processes (Long-Distance Transport: Phloem (two loading…
Transport Processes
Long-Distance Transport: Phloem
Pressure flow hypthesis
molecular pumps and active transports
important driving force
sources
sites which water and nutrients are transported
STM/CC complex
functional unit of conducting cell and one/more companion cells
two loading mechanism:
active transported
Polymer trap machanism
simple sugars diffuse into conducting cells
polymerized into polysaccharides
mass transfer
actual amount of sugars/nutrients transported by phloem
Sinks
sites that receive transported phloem sap
extremely diverse
Break/cut in sieve elements
p-protein
found as fine network adjacent to plasma membrane
p-plug
p-protein is carried to the sieve area and is to large to pass so it plugs the hole.
Uninjured phloem
cellose
solution only if under pressure
if injured causes a pressure drop
then carried with p-protein to the sieve area
Water Potential
water potential
chemical potential of water is important in botany
as a symbol pronounced "sigh"
free energy is of water
three ways energy can be decreased:
reducing pressure on it
lowering it
cooling it
Pressure potential
the effect pressure has on water potential
measured in megapascals (MPa) or bars
osmotic potential
effect solutes have on water potential
Matric potential
waters adhesion to non-dissolved structures such as cell walls
adhesion can only decrease waters free energy
Incipient plasmolysis
protoplast has lost enough water to pull away from the wall
Plasmolyzed
protoplast pulls completely ways from the wall and shrinks
Short distance Intracellular Transport
communicate with other neighboring cells
transfer water, sugars, minerals, and hormones
Symplast
all the protoplasm of one plan can be considered one continues mass
Transfer through the plasma membrane
osmosis
molecular pumps in plasma membrane
fusion between transport vesicles and plasma membrane
Guard Cells
opening/closing of stomatal pores
use potassium to open
Motor Cells
"joints"
accumulate or expel potassium
located along the midrib
Transfer Cells
exterior surface: smooth
Inner surface: numerous finger-like and ridge like outgrowth
makes more surface area
Diffusion, Osmosis, and Active Transport
Diffusion
random movement of particles from a high concentration to a low concentration
Osmosis
movement through a membrane
3 types of membranes
Completely impermeable
do not allow anything to pass
occur as isolation barriers
Selectively permeable membrane
allow only certain substances to pass
lipids/protein cell membranes are differentially permeable
Freely Permeable
allow all solutes to diffuse through them
have little biological signficance
hydrophobic molecules diffuse through any membrane
hydrophilic molecules can only pass through if a protein channel is present
intracellular transport
vesicle migrate through the cytoplasm and fuse w/another organelle
parts of the membrane
aquaporins
protein channel water moves through rapidly
molecular pumps
use ATP to force molecule across the membrane
active transport
The Water available in Water
Eutrophicaiton
algea dies, sinks, and decomposed by bacteria
uses so much oxygen fish can suffocate
prevent eutrophication by keeping phosphate levels low
water is pure coming from rain
becomes un pure by runoff and pollution
salt water
water can be evaporated but the salt will stay where it is
salt becomes concentrated
Plants/humans can not drink
will cause dehydration and death if that is the only liquid consumed
Water Available in Air
Air supplies water many ways
rain
dew
frost
snow
fog
hail
humidity
timing and regulation of precipitation is important
humidity can prevent transpiration and transport of minerals up roots
Long-Distance Transport: Xylem
Properties of water
Cohesive
Water interacts strongly with other water molecules
Adhesive
water molecules interact with many other substances
water adheres firmly to soil
Heavy
requires great deal of energy to lift to the top of a tree
Water Transport Though Xylem
Cohesion-tension hypothesis
when stomatal pores are open water loss happens
most widely acceptable model
water loss is called trans-stomatal transpiration
transcuticular transpiration
water loss directly through the cuticle
cavitaion
hydrogen bonding is broken over a large region
water column breaks
embolism
space between the two portions
Control of Water Transport by Guard Cell
Bulk movement of water through xylem
influenced and powered by water loss
