# Explain how auxin controls the growth of a plant root growing downwards in response to gravity.

> AQA GCSE Biology (8461) — 4.5.4 Plant hormones (Bio only) · Explain · 4 marks

> Plants can detect and respond to gravity. Roots show positive geotropism, growing downward into the soil.

## Mark scheme (4 marks)

1. Auxin moves to the lower side of the root (due to gravity / is redistributed unevenly)
2. There is a higher concentration of auxin on the lower side of the root
3. In roots, auxin inhibits / slows cell elongation (at higher concentrations)
4. The upper side of the root elongates more / grows faster, so the root curves downwards

## Key terms

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

## Related

- [Revision notes for AQA GCSE Biology (8461)](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-how-auxin-controls-the-growth-0e4cfde6) · Published by Druglandscape Ltd.