# Explain why a plant shoot placed in a box with a small hole on one side will grow towards the hole after several days.

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

> A gardener places a young plant shoot inside a closed box. The box has a small hole on one side, allowing light to enter from that direction only. After several days, the shoot has bent and is growing towards the hole.

## Mark scheme (4 marks)

1. Light comes from one direction (through the hole), so auxin moves/is redistributed to the shaded side of the shoot tip
2. The higher concentration of auxin on the shaded side causes cells there to elongate more
3. Cells on the lit side elongate less / grow more slowly because auxin concentration is lower there
4. Because the shaded side is longer than the lit side, the shoot bends / curves towards the light (source / hole)

## 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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