Transport Processes
Concepts
Long-Distance Transport: Phloem
Diffusion, Osmosis, and Active Transport
Water Potential
Short-Distance Intercellular Transport
Long-Distance transport: Xylem
Cells and Water Movement
Motor Cells
Transfer Cells
Guard Cells
Water Transport Through Xylem
Control of Water Transport by Guard Cells
Properties of Water
short distance transports that occur within a few cells diameter.
long distance transport between cells that are not close. But not essential in the construction of a large plant.
isolation mechanisms inhibit movement of substances.
diffusion is where the random movement of particles in solution causes them to move from a high concentration to areas of low concentration.
diffusion through a membrane is osmosis
Active transport is where molecular pumps force molecules across a membrane.
Plant cells can never absorb enough water that they burst.
water can be supplied to plants as rain, fog, dew, frost, snow, hail, and humidity.
when the plant loses a little water and the protoplast pulls slightly away from the wall it is called incipient plasmosis
when the plant loses a lot of water that the protoplast pulls away completely it is plasmolyzed
when open their potassium gives them a very negative osmotic potential which makes it have a large pressure potential.
when closed they have less potassium and only a small negative osmotic potential
they can either accumulate or expel potassium and adjust their water potential and turgidity.
transfer cells are found where rapid short distance transport is expected to occur
phloem sap is under pressure and can bleed uncontrollably if cut. two mechanisims seal broken sieve elements, P-protein and callose.
water is cohesive so any force acting on one molecule acts on neighboring ones as well.
water interacts with other substances making it adhesive
when stomatal pores are open they allow water loss
in vertical stems water must move directly upward in the xylem.
light controls guard cell water relations
blue light is the triggering wave-leangth