Closure of stomata occurs as the guard cells:
1. lose water.
2. begin photosynthesis reducing internal ${\mathrm{CO}}_2$ concentration.
3. pick up chloride ions.
4. gain potassium ions.

Guttation is:
1. deposition of dew drops on the leaves in the morning.
2. shrinking of protoplast away from the cell wall.
3. evidence of root pressure.
4. cavitation in the water column.

A column of water in the xylem even in a tall tree normally does not sink because of its weight due to:

The apoplast pathway in plants includes all the following except:
1. the lumen of a xylem vessel
2. the lumen of a sieve tube
3. the lumen of tracheids
4. the cell wall of a root hair

Osmosis in plants would not be affected by:
1. water potential gradient
2. a difference in solute concentrations
3. type of cell membrane receptor proteins
4. number of aquaporins

Active transport of substances does not involve:
1. transport of solute along the concentration gradient.
2. use of a specific membrane transport protein.
3. hydrolysis of ATP.
4. transport of solute against a concentration gradient.

The direction of water movement in plants can always be predicted by measuring:
1. pressure potential
2. number of aquaporins
3. proton gradients
4. water potential (ψ)

Give ${\mathrm{\psi }}_{\mathrm{P}}$ = 0.25 MPa and ${\mathrm{\psi }}_{\mathrm{S}}$ = -0.50 MPa,what will be the resulting Ψ:
1. +0.75 MPa.
2. -0.75 MPa.
3. -0.25 MPa.
4. +0.25 MP

Identify the correct statements regarding bulk flow in plants:
I. Driven primarily by pressure potential.
II. More effective than diffusion over greater distances.
III. Depends on the difference in pressure potential at the source and sink.
IV. Depends on the force of gravity on a column of water.
V. May be due to either positive or negative pressure potential.
1. I, II and III only
2. II, III and V only
3. II, III, IV and V only
4. I, II, III and V only.

The Casparian strip in plant roots:
1. is located in the walls of the outermost portion of the cortex.
2. is composed predominantly of lignin and hence is impermeable to water.
3. ensures active uptake of all minerals by the roots.
4. ensures that all water and dissolved substances must pass through a cell membrane before entering the vascular cylinder.