A student places a wilting pot plant into a bucket of water. Explain why the plant regains its rigidity after being watered.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Water enters the root hair cells by osmosis, increasing the water potential inside the cells.
The water is then carried up the xylem vessels to the stem and leaves.
When the water reaches the leaf cells it raises their internal water potential, so water flows into the cells.
The increased water content raises turgor pressure, restoring cell rigidity and the plant regains its stiffness.
The water is then carried up the xylem vessels to the stem and leaves.
When the water reaches the leaf cells it raises their internal water potential, so water flows into the cells.
The increased water content raises turgor pressure, restoring cell rigidity and the plant regains its stiffness.
Examiner tips
- Use the term ‘osmosis’ for water movement into root hairs. Mention the xylem as the conduit for upward transport. Explain that increased turgor pressure is what gives rigidity. Show the cause–effect chain: water uptake → turgor rise → rigidity restored.
Common mistakes
- Confusing water potential with pressure potential. Forgetting to mention the xylem. Saying the plant regains rigidity because it is ‘wet’ rather than because of turgor pressure. Using ‘transpiration’ without linking it to water loss.
Mark scheme (4 marks)
- Water enters root hair cells by osmosis
- Water moves into the xylem and up the stem to the leaves / cells
- Water enters cells, increasing turgor pressure
- Wilting occurred because water loss via transpiration exceeded water uptake, and watering reverses this / restores water content
Key terms in this question
Related
- All Cambridge International IGCSE Biology (0610) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →