# Explain why the rate of transpiration from a leafy shoot is higher on a hot, dry, windy day than on a cool, humid, still day.

> Pearson Edexcel International GCSE Biology (4BI1) — 2.10 Transport: flowering plants · Explain · 4 marks

## Mark scheme (4 marks)

1. Higher temperature increases the rate of evaporation of water from the mesophyll cells (into the air spaces)
2. Dry air / low humidity maintains a steep concentration gradient for water vapour between the leaf air spaces and the surrounding air
3. Wind removes water vapour from around the leaf surface, maintaining or increasing the concentration gradient
4. Water vapour diffuses out of the leaf through the stomata (down the concentration gradient), so a steeper gradient / faster evaporation leads to a higher rate of transpiration

## Key terms

- [transpiration](https://www.gradenine.co.uk/glossary/transpiration)

## Related

- [Revision notes for Pearson Edexcel International GCSE Biology (4BI1)](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-why-the-rate-of-transpiration-44216f56) · Published by Druglandscape Ltd.