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Transport Processes (Long-distance transport: phloem (two mechanisms (P…
Transport Processes
Long-distance transport: phloem
pressure flow hypothesis
water and nutrients are moved
sources
the site that water and nutrients are transported from
actively transported
sieve elements
polymer trap mechanism
conducting-cell plasma membranes
loads phloem
STM/CC complex
conducting-cell, one or several companion cells
mass transfer
sugars and nutrients
transported by phloem
specific mass transfer
cross-sectional area of phloem
sinks
sites that recieve transported phloems sap
two mechanisms
P-protein
fine network adjacent to plasma membrane
P-protein plug
P-protein mass is too big to pass through
Callose
polymer
under pressure
precipitates into a flocculent mass
Water potential
cells and water movement
water doesn't move between cells
cell neither shrinks nor swells
water potential
the chemical potential for botany
pressure potential
the effect that pressure has on water
megapascals
units of pressure
osmotic potential
effect that solutes have on water
the value of 0.0 MPa
matric potential
water adhesion to nondissolved structures
cell walls
membranes
soil particles
always negative
Diffusion, osmosis, and active transport
diffusion
random movement of particles in solution
osmosis
diffusion through a membrane
aquaporins
protein channels
molecular pumps
force molecules across the membrane
active transport
recieving side of membrane
Short-distance intercellular transport
guard cells
opening or closing of stomatal
night
stomata are closed
guard cells are shrunken
open right at sunlight
motor cells
similar to guard cells
accumulate or expel potassium
transfer cells
inner surface
numerous finger-like outgrowths
outer surface
walls are smooth
symplast
protoplasm of one plant
one continuous mass
apoplast
molecules move through
the cell wall
the intercellular space
Long-distance transport: xylem
properties of water
based on simple properties of water and solutions
adhesive
molecules interact with many substances
cohesive
force acting on one molecule
water transport through xylem
cohesion-tension hypothesis
most widely accepted model
stomatal pores are open
apoplastic space of spongy mesophyll
are filled with
moisture-saturated air
transstomatal transpiration
water loss
warm air can have a negative water potential
transcuticular transpiration
water is lossed through cuticle
by being hydrophobic
allowing very little water loss
control of water transport by guard cells