# A farmer wants to use a plant hormone to control weeds growing among their crop plants. Explain how auxins can be used as selective weedkillers to kill the weeds without harming the crop.

> Edexcel GCSE Biology (1BI0) — 6.3 Plant hormones · Explain · 4 marks

> Broad-leaved weeds, such as dandelions, often compete with narrow-leaved cereal crops for resources. Farmers can spray fields with synthetic auxins to remove these weeds.

## Mark scheme (4 marks)

1. Auxins are plant hormones that stimulate growth in shoots
2. When sprayed in high concentrations, auxins cause uncontrolled/excessive growth in broad-leaved weeds
3. This excessive growth kills the broad-leaved weeds
4. Narrow-leaved crop plants are not affected / absorb less auxin, so they are unharmed

## Key terms

- [auxins](https://www.gradenine.co.uk/glossary/auxins)
- [selective weedkillers](https://www.gradenine.co.uk/glossary/selective-weedkillers)

## 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/a-farmer-wants-to-use-a-456aba39) · Published by Druglandscape Ltd.