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GCSE Biology · key term
A directional growth response of a plant to a stimulus.
Used by AQA, Edexcel and OCR
Specification 4.5.4.1 · Paper 2
Revise: Plant Control and CoordinationA tropism is a directional growth response to a stimulus. Growth towards a stimulus is positive; growth away from it is negative. Light produces phototropism, while gravity produces gravitropism (also called geotropism).
Specification 6.15B · Paper 2
A directional growth response by a plant to a stimulus.
Use the direction of growth—not the position of the stimulus—to classify a tropism: growth towards a stimulus is positive; growth away is negative.
Do not say that a shoot moves towards light. A tropism is directional growth, produced because one side elongates more than the other.
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A tropism is a directional growth response to a stimulus.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
A directional growth response by part of a plant to a stimulus.
Revise: Plant HormonesA growth response whose direction depends on the direction of a stimulus is a tropism. Growth towards a stimulus is positive; growth away from it is negative. Because the response is caused by growth, it is usually much slower than an animal movement.