The cells of a certain plant species can accumulate solutes to create very low solute potentials. Which of these statements is correct?
a. The plant's transpiration rates will tend to be extremely low.
b. The plant can compete for water effectively and live in relatively dry soils.
c. The plant will grow most effectively in soils that are saturated with water year-round.
d. The plant's leaves will wilt easily.

A mutant plant lacking the ability to pump protons out of leaf companion cells will be unable to do which of the following?

a. Initiate transpiration

b. Load sucrose into sieve-tube elements

c. Carry out photosynthesis

d. Transport water through the xylem

What important role does the Casparian strip play in the movement of water through plants?

a. Forces water to move through the cytoplasm of living endodermal cells as it makes its way from the soil to the xylem

b. Causes cells to shrink, thereby increasing pressure within cells

c. Loads sugars into xylem, thereby causing water to enter the xylem by osmosis

d. Acts as a filter that prevents salts, heavy metals, and other pollutants from entering root hairs

Consider the following statements regarding the transport of phloem sap. Select True or False for each statement.

T/F This is a passive process that is driven by the evaporation of water from leaves.

T/F Sugars tend to move from sources to sinks.

T/F Phloem sap moves through sieve-tube elements under positive pressure.

T/F Sieve-tube elements and vessel elements are commonly involved in the transport of phloem sap.

What is the role of companion cells in the movement of sugars through plants?

a. They are the sites of sugar production by photosynthesis.

d. They are the sites where starch is converted to sucrose.

c. They secrete sucrose, which draws sugars through phloem under negative pressure.

d. They accumulate sucrose, which is then transferred to adjacent sieve-tube elements.

Your friend claims that phloem always carries sugars down a plant. What, if anything, is wrong with that statement?

Draw a plant cell in pure water. Add dots to indicate solutes inside the cell. Now add more dots to indicate an increase in solute potential inside the cell. Add an arrow showing the net direction of water movement in response. Add arrows showing the direction of wall pressure and turgor pressure in response to water movement. Repeat the same exercise, but this time, add solutes to the solution outside the cell at a concentration that is greater than inside the cell.