Plant hormones: GCSE Biology
Tropisms, auxin, required practical, gibberellins, ethene and commercial uses
The short version
Auxin causes phototropism and gravitropism; gibberellins and ethene have commercial uses such as ripening and germination.
Key idea
Grade 2–3: Plants grow towards the light and roots grow down into the soil.
Grade 5–6: I can use positive/negative and photo/gravi.
Grade 9: I say growth response (not "the plant walks") and I set up auxin as the unequal-growth explanation.
Go a bit deeper
Same hormone, opposite effect - that is the Grade 9 mark
Grade 2–3: The dark side of the stem grows faster so it tips towards the window.
Grade 9: I can do roots as well: auxin collects on the lower side and slows growth there. I never say auxin "runs away from light like legs".
Question: Explain why a shoot bends towards the light. [4 marks] [4 marks]
Worked example
Worked example
Grade 2–3: Plants grow towards the light and roots grow down into the soil. Grade 5–6: I can use positive/negative and photo/gravi. Grade 9: I say growth response (not "the plant walks") and I set up auxin as the unequal-growth explanation.
Lessons in this topic
- Tropisms
- Auxin
- Required practical: phototropism
- Gibberellins and ethene
- Commercial uses of plant hormones
- Weedkillers and evaluation
In the app each lesson is video (when we have a real YouTube id) then intro, learn and summary steps.
What the examiner wants
Explain unequal auxin distribution in tropisms, describe the phototropism practical, and apply hormone uses to crop questions.
Try these questions
Cover the answers and have a go first. Worked solutions are underneath.
A shoot growing towards light is
Auxin is produced mainly in the
In a shoot with light from one side, auxin
In roots, high auxin
Common mistakes
- Tropisms are not the same as nasties (folding) and not animal reflexes. Do not give the plant a brain.
- Do not say the light side grows more. The shaded side grows more. And do not give shoots and roots the same auxin effect.
- A single seedling on a windowsill is not a required-practical method. No control, no measurement, no repeats.
- Ethene is not ethane and not ethanol. Wrong organic word, wrong mark.
Answers and working
Frequently asked questions
Is GCSE Plant hormones on Combined Science and Triple?
Plant hormones is Triple-only Biology. Combined Science students can skip it.
Which exam board is this Plant hormones page for?
The ideas are board-agnostic for AQA, Edexcel, OCR, WJEC and CCEA. Paper lengths and question numbers differ — check your specification.
Is Plant hormones Foundation or Higher?
The core ideas appear on both tiers. Higher papers add extra application and some HT-only detail, marked in lessons with a Higher badge.
Learn, try, get feedback, fix the mistake
Open the stepped lesson, then the quiz with hints. Required-practical and calculation questions use the same method you will need in the paper.
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