# A seedling is grown in a windowless box. A small hole is cut in one side of the box so that light enters from one direction only. After several days, the shoot tip is removed from the seedling and the seedling is left to continue growing. Explain why the shoot no longer bends towards the light after the tip has been removed.

> Cambridge International IGCSE Biology (0610) — 14.5 Tropic responses · Explain · 4 marks

> A seedling is grown in a windowless box with a small hole cut in one side, so that light enters from one direction only. After several days, the shoot tip is removed.

## Mark scheme (4 marks)

1. Auxins are produced at the shoot tip
2. Without the tip, no auxins are produced / auxins are absent
3. Auxins normally move to / accumulate on the shaded side of the shoot, causing unequal growth
4. Without auxins there is no differential / unequal growth, so the shoot grows straight / does not bend

## Key terms

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

## Related

- [Revision notes for Cambridge International IGCSE Biology (0610)](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-seedling-is-grown-in-a-b8e429ed) · Published by Druglandscape Ltd.