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Ch. 12 Transport Processes (Short-Distance Intercellular Transport (Guard…
Ch. 12 Transport Processes
Concepts
short-distance transport
#
transfer of basic nutrients
long-distance transport
not absolutely essential in construction of large plants
isolation mechanisms
inhibit movement of substances
Casparian strips
epidermus
essential for useful transport
Diffusion, Osmosis, and Active Transport
diffusion
osmosis
through membrane
freely permeable
allow all solutes to pass
completely impermeable
nothing passes through
selectively permeable
only certain things can pass
molecular pumps
use ATP for pump
active transport
intracellular transport
vesicles migrate through cytoplasm
fuse with another organelle
Water Potential
Cells and Water Movement
lysis
cells that burst when placed in water
incipient plasmolysis
protoplast has lost enough water to pull away from wall
plasmolyzed
when incipient plasmolysis does not happen
protoplast pulls completely from wall and shrinks
sigh (unit used)
Ψ=Ψpi+Ψp+Ψm
pressure potential equation
Ψpi
osmotic potential
#
Ψm
matric potential
measured in megapascals MPa (bars)
Short-Distance Intercellular Transport
Guard Cells
opening and closing of stomatal pores
night closed
day open
Motor Cells
cells at "joints"
venus flytrap slowly opening
Transfer Cells
molecular pumps
located where rapid short distance transport occurs
secrete salt
nutrients to embryos
sugar loaded in/out phloem
symplast
one mass of protoplasm
apoplast
small molecules that can go through wall and intercellular spaces
Long-Distance Transport: Phloem
pressure flow hypothesis
molecular pumps and active transport are important driving forces
sources
sites where water and nutrients are transported
spices and sugars
actively transported
sinks
receive transported phloem sap
P-protein
becomes tangled mass in cell center
P-protein plug
callose
extremely diverse
polymer trap mechanism
phloem is loaded
conducting-cell plasma membrane permeable to monosaccharides and disaccharides
not to polysaccharides
STM/CC complex
conducting cell and companion cells
phloem transport
mass transfer
sugars and nutrients transported per hour
specific mass transfer
mass transfer / cross-sectional area
Long-Distance Transport: Xylem
Properties of Water
cohesive
strong water bonds
adhesive
water molecules interact with other water
Water Transport Through Xylem
cohesion-tension theory
#
open stomatal pores allows water loss
transstomatal transpiration
transcuticular transpiration
directly through cuticle
poikilohydry
body water content that changes with habitat moisture
cavitation
water column breaks
hydrogen bonding broken over large region
embolism
space between two portions
air bubble
Control of Water Transport by Guard Cells
open stomata
trade between CO2 and H2O
light and CO2 normal conditioning
what is osmosis?
vs.
H2O bonds
