How many of the following processes involve active transport across membranes in plants?
I. the movement of mineral nutrients from the apoplast to the symplast.
II. the movement of sugar from mesophyll cells into sieve-tube members in maize.
III. the movement of sugar from one sieve-tube member to the next.
IV. K⁺ uptake by guard cells during stomatal opening.
V. the movement of mineral nutrients into cells of the root cortex.
1. 2
2. 3
3. 4
4. 5

All the following statements regarding root hair in plants are true except:

Root hair cells have ${\mathrm{H}}^{+}$ pumps that:
1. establish ATP gradients
2. acquire minerals from the soil
3. pressurize xylem transport
4. eliminate excess electrons

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.

Translocation in xylem will not be facilitated by:
1. The cohesion of water molecules.
2. A negative water potential.
3. The root parenchyma.
4. The active transport of solutes.

It is a common observation that pine seedlings grown in sterile potting soil grow much slower than seedlings grown in soil from the area where the seeds were collected. The most probable cause for this would be:

The flow of water through the xylem is regulated by:
1. passive transport of mineral ions by the root endodermis.
2.the number of nuclei in the companion cells in the phloem.
3. the evaporation of water from the leaves.
4. active transport by tracheid and vessel elements.

The pressure component of water potential most often would be negative in:
1. leaf mesophyll cell
2. stem xylem
3. stem phloem
4. root cortex cell

Which of the following is a common adaptation in aquatic plants?
1. chlorenchyma
2. aerenchyma
3. colenchyma
4. hydrenchyma

Cohesion of water molecules is due to:
1. a high latent heat of vaporization of water
2. higher density of liquid water than solid water
3. hydrogen bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule
4. covalent bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule