Syllabus Edition

First teaching 2023

First exams 2025

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Phototropism (HL) (HL IB Biology)

Revision Note

Cara Head

Author

Cara Head

Expertise

Biology

Phototropism

  • Plant shoots are positively phototropic, meaning they grow towards light (negative tropisms are those where the plant grows away from the stimulus)
  • This ensures plants maximise the amount of light they can absorb for photosynthesis
  • Phototropism affects shoots and the top of stems
  • This is an important mechanism of plants due to their immobility

Positive Phototropism Diagram

Parsley phototropism

Positive phototropism leads to plants growing toward a light source

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Cara Head

Author: Cara Head

Cara graduated from the University of Exeter in 2005 with a degree in Biological Sciences. She has fifteen years of experience teaching the Sciences at KS3 to KS5, and Psychology at A-Level. Cara has taught in a range of secondary schools across the South West of England before joining the team at SME. Cara is passionate about Biology and creating resources that bring the subject alive and deepen students' understanding