Exchange and transport in plants Quiz
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1. Which of the following correctly describes the structure and function of xylem tissue?
- A. Xylem consists of living cells that transport water and mineral ions from the roots to the leaves
- B. Xylem consists of dead cells with thickened walls that transport water and mineral ions from the roots to the leaves
- C. Xylem consists of living cells that transport sugars from the leaves to other parts of the plant
- D. Xylem consists of dead cells that transport both water and sugars throughout the plant
2. A student uses a potometer to investigate transpiration rates. The water level in the potometer falls faster on a hot, dry, windy day compared to a cool, humid, still day. Which factor is most directly responsible for this difference?
- A. The plant has more leaves on hot days
- B. Higher temperature increases water evaporation from the leaves, and lower humidity and wind speed increase the rate at which water vapour is removed from around the leaves
- C. Wind speed alone is the only factor affecting transpiration rate
- D. The plant's roots absorb more water on hot days
3. Explain why the structure of phloem cells allows them to transport sucrose effectively, whereas xylem cells cannot perform this function.
- A. Phloem cells are living and have companion cells that provide energy (ATP) for active transport of sugars, whilst xylem cells are dead and cannot carry out active transport
- B. Phloem cells have thickened walls that prevent sugar loss, whilst xylem cells have thin walls
- C. Phloem cells are wider than xylem cells, allowing larger sugar molecules to pass through
- D. Xylem cells contain chlorophyll which prevents sugar transport, whilst phloem cells do not
4. Water moves through a plant from the roots to the leaves in the transpiration stream. Which statement best explains how this movement occurs?
- A. Root cells push water upwards using active transport
- B. Water is pulled upwards due to transpiration in the leaves creating a water potential gradient, and water molecules form a continuous column in the xylem held together by cohesion
- C. Osmosis in the leaves pulls water upwards through the xylem vessels
- D. Water moves upwards because xylem cells are living and contract to pump water
5. At higher tier, translocation involves the transport of sucrose and amino acids through phloem tissue. How does the rate of translocation differ from the rate of transpiration, and why?
- A. Translocation is much faster than transpiration because phloem cells are living and use active transport, whereas transpiration is a passive process driven by evaporation
- B. Translocation is much slower than transpiration because it requires active transport and the transport of large molecules, whereas transpiration is a passive process driven by water evaporation
- C. Translocation and transpiration occur at the same rate because they both involve water movement in xylem vessels
- D. Translocation is faster because sugars move more quickly than water molecules