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Transport Processes (Short-Distance Intercellular Transport (Most plant…
Transport Processes
Short-Distance Intercellular Transport
Motor Cells
Cells at "joints"
Can either accumulate or expel:
Potassium & adjust their water potential & turgidity
Transfer Cells
The larger the membrane, then:
The more molecular pumps it can hold
Walls are smooth on the outer surface but have:
Finger-like & ridge-like outgrowths on the inner surface
Guard Cells
Opening & closing of stomatal pores
At night,
These cells are shrunken & have little internal pressure
During the day,
Potassium ions are actively transported into guard cells
Most plant cells communicate with their:
Transferring water
Sugars
Neighboring cells
Hormones
MInerals
Long-Distance Transport: Phloem
Sources:
Sites where water and nutrients are transported
Polymer trap mechanism:
Conducting-cell plasma membranes are permeable to,
monosaccharides & dissaccharides but not to polysaccharides
Sinks:
Sites that receive transported phloem sap
Extremely diverse
Diffusion, Osmosis, & Active Transport
Osmosis
Diffusion through a membrane
Three types of membranes
Freely permeable
Allows all solutes
Completely permeable
Does not allow anything
Differentially or selectively permeable
Allows only certain substances to pass
Active Transport
Use the energy of ATP
To force molecules across the membrane
A protein helps change change the shape of the molecule
To allow it to cross the membrane
Diffusion
Random movement of particles in solution
Causes them to move from high concentration to low
Water Potential
Cells & Water Movement
Free energy of water
Can be increased in several ways:
Put under pressure
Elevated
Heated
Can be decreased by:
Reducing pressure on it
Lowering it
Cooled
Types of potential
Pressure potential
Effect that pressure has on water potential
Osmotic potential
Effect that solutes have on water potential
Water potential
Free energy of water
Matric potential
Adhesion that can only decrease water potential
Long-Distance Transport: Xylem
Water Transport Through Xylem
When stomatal pores are open,
they unavoidably allow water loss
At night,
Xylem water pressure increases, &
gases may dissolve back into the solution
Control of Water Transport by Guard Cells
When stomatal pores are open,
Transstomatal transpirtaion is more significant
If soil is too dry to supply water,
Transpiration represents an immediate potentially lethal threat
Which is due to dessication
Properties of Water
Water molecules interact strongly w/ other water molecules
Adhesive
Its molecules interact with many other substances
Cohesive
Interacting strongly w/ other water molecules
