Edexcel IGCSE Biology · Spec 2.83-2.85
Plant Responses Tropisms
Tropisms in plants — phototropism and gravitropism — and how the hormone auxin controls growth.
Biology revision video
Plant Responses Tropisms
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Spec 2.83-2.85
What you need to know
- Explain what a tropism is
- Describe phototropism and the role of auxin
- Describe gravitropism, also called geotropism
Active recall
Quick check
Answer each question before opening the answer.
How do shoots and roots respond to light and gravity?
Shoots grow towards light (positive phototropism) and away from gravity; roots grow towards gravity (positive gravitropism) and away from light.
Which hormone controls these growth responses?
Auxin.
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