Year 11 - Science
Auxins, phototropism and gravitropism
Plant growth and development
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
This unit covers the role of plant hormones like auxins, gibberellins, and ethene in growth and development, including phototropism and gravitropism. It explores their commercial uses and focuses on experiments, data analysis, and presenting scientific explanations.
Lesson Summary
You will learn to explain how hormones called auxins cause plant shoots and roots to respond to light and gravity.
Key Notes
- Hormones control growth and development in plants, and enable plants to respond to some environmental factors.
- Auxins are plant hormones that control tropisms, which are growth responses in plants that provide a survival advantage.
- Phototropism in a shoot: auxins build up on the shaded side and cause cell elongation, so it bends towards the light.
- Gravitropism in a shoot: auxins build up on the lower side and cause cell elongation, so it bends upwards.
- Gravitropism in a root: auxins build up on the lower side but this stops cell elongation, so it bends downwards.
Vocabulary To Learn
- hormone: chemicals released by plants that regulate their growth
- auxins: control the growth of plants by promoting cell division and elongation in plant cells
- tropism: a plant growth response to a stimulus, it can be positive (towards) or negative (away from)
- phototropism: a plant growth response towards or away from light
- gravitropism: a plant growth response towards or opposite the direction of gravity
Common Mistakes To Avoid
- Pupils may think that plants move towards the sun, rather than grow in that direction. Pupils may also think that plants are not living.
3 Quick Questions (With Answers)
1. Explain the scientific idea in this lesson using two key points.
Hormones control growth and development in plants, and enable plants to respond to some environmental factors. Auxins are plant hormones that control tropisms, which are growth responses in plants that provide a survival advantage.
2. Define this scientific word and use it in context. 'hormone'
chemicals released by plants that regulate their growth. Include the word in a full scientific explanation, not as a single label.
3. Correct this common scientific misunderstanding.
Mistake: Pupils may think that plants move towards the sun, rather than grow in that direction. Pupils may also think that plants are not living. Correction: Plants grow in a certain direction through mitosis (in meristem) and elongation. Plants are living as they carry out the common processes of living organisms.
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