This deep dive covers Auxin — How It Works within Plant Hormones for GCSE Biology. Topic 11: Plant Hormones It is section 2 of 12 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
🔬 Auxin — How It Works
Auxin is a plant hormone that controls growth:
- Made in shoot tips and root tips
- Causes cell elongation (cells grow longer)
- Moves away from light in shoots
- High concentration in shoots = more growth
- High concentration in roots = less growth (roots are more sensitive)
Phototropism explained:
- Light hits shoot from one side
- Auxin moves to shaded side
- Cells on shaded side elongate more
- Shoot bends towards light
Practice questions for Plant Hormones
When a plant shoot is lit from one side, where does auxin accumulate?
Explain how auxin causes gravitropism (geotropism) in plant roots.
Quick recall flashcards
What is gravitropism?
Gravitropism is the growth response of a plant to gravity. Roots show positive gravitropism (grow downward, towards gravity). Shoots show negative gravitropism (grow upward, away from gravity).
What is phototropism?
Phototropism is the growth response of a plant to light. Shoots show positive phototropism — they grow towards the light source.