Explain how water moves from the soil into the xylem of a plant root, and describe how the xylem is adapted to transport water to the leaves.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Root hair cells absorb water from the soil.
Root hair cells have a large surface area (long hair‑like extensions) to increase the rate of absorption.
Xylem transports water and dissolved minerals from the roots to the leaves.
Xylem cell walls are strengthened by lignin, forming hollow tubes that support the upward flow of water.
Root hair cells have a large surface area (long hair‑like extensions) to increase the rate of absorption.
Xylem transports water and dissolved minerals from the roots to the leaves.
Xylem cell walls are strengthened by lignin, forming hollow tubes that support the upward flow of water.
Examiner tips
- Use the word ‘root hair cells’ and mention their large surface area. Mention that xylem carries water and minerals. State that lignin‑reinforced hollow tubes allow upward transport.
- Include all four points to reach full marks.
Common mistakes
- Confusing xylem with phloem. Omitting the role of lignin or the hollow tube structure. Using vague terms like ‘root cells’ instead of ‘root hair cells’.
Mark scheme (4 marks)
- Root hair cells absorb water from the soil
- Root hair cells have a large surface area (due to long hair-like extensions / root hairs) to increase the rate of absorption
- Xylem transports water and dissolved minerals from the roots to the leaves
- Xylem cell walls are strengthened / reinforced by lignin, forming hollow tubes that support the upward flow of water
Key terms in this question
Related
- Revision notes: Transport in plants →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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