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Transport Process (Long-Distance Transport Phloem (Pressure flow…
Transport Process
Long-Distance Transport Phloem
Pressure flow hypothesis
may be the mechanism by which water and nutrients are moved through phloem
Sources
sites where water and nutrients are transported
Actively transported
Spicies and sugars are transported into sieve elements
Polymer trap mechanism
where phloem is loaded
STM/CC complex
Conducting cell and one or several companion cells
Mass Transfer
amount of sugars and other nutrients transported by phloem
Specific mass transfer
mass transfer can be divided by cross sectional area of phloem
Sinks
sites that receive transported phloem sap and extremely diverse
P-protein
fine network adjacent to the plasma membrane inner surface of uninjured sieve elements
P-protein plug
P-protein that is too large to pass through sieve area
Callose
prevents leaking
Diffusion, Osmosis, and Active Transport
Diffusion
Movement of particles from high concentrations to low concentrations
Osmosis
Diffusion through the membrane
Freely permeable
membranes that allow all solutes to diffuse through them
Completely impermeable
membrane that doesn't allow anything to pass through
Selectively permeable membranes
allows only certain substances to pass through
Aquaporins
protein channels in membranes
Molecular pumps
uses Atp to force molecules across the membrane
Active Transport
when molecules are pumped across a membrane using ATP even to a high concentration area
Intracellular Transport
vesicles migrate through cytoplasm and fuse with another organelle
Water Potential
Water Potential
Chemical potential of water
Pressure Potential
the effect that pressure has on water potential
Megapascals (Bars)
Units that measures potential
Osmotic potential
the effect that solutes have on water potential
Matric Potential
water's adhesion to nondissolved structures such as cell walls
Incipient Plasmolysis
protoplast has lost just enough water to pull away from the wall
Plasmolyzed
the cell continues to lose water and completely pull away from the wall and shrinks
Short-Distance Intercellular Transport
Symplast
all protoplasm of one plant considered one continuous mass
apoplast
wall and intercellular spaces
Guard Cells
Motor Cells
Transfer Cells
Long-Distance Transport Xylem
Properties of Water
Cohesive
any force acting on one molecule acts on all neighboring ones
Adhesive
water molecules interact with many other substances
Water Transport Through Xylem
cohesion-tension hypothesis
water movement through xylem and plants as a whole
transstomatal transpiration
humid air absorbing water
transcuticular transpiratioin
water lose directly through the cuticle
Poikilohydry
body water content that changes with habitat moisture
Cavitation
Hydrogen bonding is broken over a large region and water column breaks
Embolism
spaces above and below cavitation
