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34 Cards in this Set

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what is water potential?
The potential energy that water has in a particular environment compared to control condition
What always flow from area of ___ potential to areas of ___ potential
high, low
What is the water potential gradient?
The movement of water when water potential differences within a series are contrasted
What factors affect water potential?
Osmosis, solute/osmotic potential, Turgor pressure, pressure potential
What is osmosis?
The diffusion of water across membranes in response to differences in water potential
How do you calculate water potential?
Pressure potential + solute potential
What is solute/osmotic pressure?
difference in solute concentrations between two cells
What is turgor pressure?
The force of the cell membrane swelling and pushing against the cell wall
What is pressure potential?
the sum of all the types of pressures on water
What is a megapascal (MPa)?
unit of measurement for pressure
If the water potential in the space that surrounds a cell drops. What which direction will the water go and what will the cell do?
water moves out of the cell and the cell shrinks
Why do plants tend to gain water from the soil and lose it to the atmosphere?
Because water movies along the water potential gradient
How does water move up a tree?
Water is carried up a tree through the xylem tissue in a process called transpiration. Constant evaporation from the leaf creates a flow of water from root to shoot. The roots of a tree absorb the vast majority of water that a tree needs. The properties of cohesion and adhesion allow the water to move up a tree regardless of its height. Cohesion allows the individual water molecules to stick together in one continuous stream. Adhesion permits the water molecules to adhere to the cellulose molecules in the walls of xylem cells. When the water reaches a leaf, water is evaporated, thus allowing additional water molecules to be drawn up through the tree.
What are the three ways that water can reach the vascular tissue?
transmembrane route, apoplast, symplast
What is the Casparian strip?
It prevents water from creeping through the walls of the enodermal cells
What is responsible for Root pressure?
endodermi
what is guttation?
Water droplets forced out of leaves
How does water move in the capillaries? (three forces)
Surface tension, adhesion, cohesion
What is surface tension?
Downward pull that exist on water molecules at an air-water interface
What is adhesion?
the attraction of unlike molecules
What is cohesion?
mutual attractions amoung like molecules,
According to the Cohesion-Tension Theory what happens to tree trunks because of water tension?
They shrink
What is the most important features of the cohesion-tension theory?
It does not require the expenditure of energy
How does a plant do to limit water loss?
1 Thick cuticule on the upper surface of the leaves
2. Several layers of epidermis
3. stomata located in deep pits on the undersides of leaves.
How do the stomata open and close?
Each stoma has two bean shaped guard cells which have thich inner walls.During daytime, they get filled with water, due to which they bulge out and thus open. At nightime, they lose the water. Hence, they lose their turgidity and close.
What is Crassulacean acid metabolism?
plants open their stomata at night and store the CO2 that diffuse into their tissues by adding organic acides
What is translocation?
The movement of sugars through a plant
What is a sink?
a tissue where sugar exits the phloem
What is a sieve plate?
The perforated end wall
What is the pressure flow hypothesis?
The events at source tissues and at sink tissues create a steep pressure potential gradient
How is sucrose and other solutes transported across Membranes?
Passive transport, facilitated diffusion, active transport
What is bulk flow?
a mass movement of molecules along a pressure gradient
How are sugars concentrated in Sieve-tube members at sources?
phloem loading
That is phloem loading?
sugar is loaded into sieve-tube elements against a concentration gradient