IGCSE Biology glossary
Tropism
Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
A growth response of a plant in which the direction of growth is determined by the direction of the stimulus. Phototropism responds to light, gravitropism to gravity.
What to include in an exam answer
The word 'growth' must appear. Tropisms are growth responses, not movements. The Extended explanation uses auxin: it accumulates on the shaded side of a shoot, that side elongates faster, and the shoot bends toward the light.
Example in context
Explaining a shoot bending to light: 'Auxin gathers on the shaded side, which grows faster, so the shoot bends towards the light. A positive phototropism.'
Related syllabus topic
Coordination & responseRelated terms
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- Negative feedback
- Reflex arc
- ADH
- Insulin
- Glucagon
- Adrenaline
- Synapse
- Neurone
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- Motor neurone
- Relay neurone
- Receptor
- Effector
- Cornea
- Iris
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- Hormones
- Endocrine gland
- Auxin
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