# Describe how auxin is distributed in a shoot tip that is receiving light from one direction only, and explain how this distribution leads to a change in the direction of growth of the shoot.

> Pearson Edexcel International GCSE Biology (4BI1) — 2.14 Coordination and response: flowering plants · Describe · 4 marks

## Mark scheme (4 marks)

1. Auxin is produced at the tip of the shoot
2. Auxin moves away from the light / accumulates on the shaded / darker side of the shoot
3. The higher concentration of auxin on the shaded side causes greater / faster cell elongation on that side
4. Unequal elongation causes the shoot to bend / curve towards the light (phototropism)

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Biology (4BI1)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-auxin-is-distributed-in-6457672f) · Published by Druglandscape Ltd.