Quiz Chapter 4: Transport in Plants

1. During phloem loading, what occurs immediately after sucrose is actively loaded into sieve tube elements at the source?

1. Water potential in sieve tubes drops, causing water to enter from xylem by osmosis.
2. Hydrostatic pressure in sieve tubes decreases to zero.
3. Stomata close instantly to prevent water vapor loss.
4. Phloem sap freezes and forms solid starch granules.

2. Which property of water allows it to adhere to the inner lignified walls of xylem vessels?

1. Adhesion
2. Cohesion
3. Viscosity
4. Surface tension

3. What structural feature connects companion cells directly to sieve tube elements?

1. Hydathodes
2. Plasmodesmata
3. Casparian strips
4. Lignified pits

4. How does water move from cell to cell via the symplast pathway in root cortex cells?

1. By moving along external cell walls only
2. Through cytoplasmic connections called plasmodesmata
3. Via active transport protein pumps in cutin layers
4. By bulk flow driven by mechanical contraction

5. What phenomenon causes droplets of water to exude from hydathodes at leaf margins?

1. Transpiration
2. Guttation
3. Plasmolysis
4. Translocation

6. What creates the high hydrostatic pressure at the source end of a sieve tube in the pressure-flow model?

1. Active pumping of oxygen into phloem
2. Inflow of water by osmosis following active sucrose loading
3. Evaporation of water through open stomatal pores
4. Movement of starch into companion cells

7. What is the function of aquatic plants like Water Hyacinth (Eichhornia crassipes) in phytoremediation?

1. Absorbing heavy metals and pollutants from contaminated aquatic ecosystems
2. Releasing high concentrations of toxic methane gas into water
3. Consuming aquatic animal larvae through parasitic roots
4. Increasing water salinity to eliminate bacteria

8. Which forces maintain a continuous, unbroken column of water in narrow xylem vessels during transpiration?

1. Gravity and root pressure
2. Cohesion between water molecules and adhesion to xylem walls
3. Active transport and endosmosis
4. Phloem mass flow and stomatal resistance

9. Which structural modification enables xylem vessel elements to withstand negative pressure without collapsing?

1. Suberin rings in the middle lamella
2. Lignified secondary cell walls
3. Perforated sieve plates with companion cells
4. Thick waxy cutin layers

10. Under which conditions is guttation most likely to occur?

1. Hot, windy, and dry sunny afternoon
2. Cool, highly humid night with moist soil
3. Freezing winter conditions with dry air
4. Bright daylight with fully open stomata