This topic summary covers Knowledge Organiser within Plant Hormones for GCSE Biology. Topic 11: Plant Hormones It is section 11 of 12 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 11 of 12
Practice
15 questions
Recall
20 flashcards
Knowledge Organiser
Key Terms
- Auxin: Controls cell elongation; moves to shaded side of shoot
- Phototropism: Growth response to light; shoots positive
- Gravitropism: Growth response to gravity; roots positive (down)
- Gibberellin: Promotes germination, stem elongation, fruit size
- Ethylene: Gas hormone; promotes fruit ripening
- Cell elongation: Auxin increases length of shoot cells; inhibits root cells
Must-Know Facts
- Auxin in shoots: high concentration = more elongation = grows toward light
- Auxin in roots: high concentration = less elongation (opposite to shoots)
- Light from one side → auxin moves to shaded side → unequal growth → bending
- Commercial uses: auxins (weedkillers, rooting powder), gibberellins (germination, fruit size), ethylene (fruit ripening)
- Phototropism = response to light; Gravitropism = response to gravity
- Shoots: positive phototropism, negative gravitropism; Roots: negative phototropism, positive gravitropism