# Explain the roles of stomata and guard cells in controlling water loss from a plant leaf.

> Edexcel GCSE Biology (1BI0) — 6.2 Transport in plants · Explain · 4 marks

## Mark scheme (4 marks)

1. Stomata are small holes/pores on the surface of a leaf through which water vapour can be lost by diffusion/evaporation (transpiration).
2. Guard cells control whether the stomata are open or closed.
3. When guard cells take in water they become turgid, causing the stomata to open, increasing water loss.
4. When guard cells lose water they become flaccid, causing the stomata to close, reducing water loss.

## Key terms

- [stomata](https://www.gradenine.co.uk/glossary/stomata)
- [guard cells](https://www.gradenine.co.uk/glossary/guard-cells)

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-the-roles-of-stomata-and-ecff8789) · Published by Druglandscape Ltd.