Explain why plants need both stomata and a waxy cuticle on their leaves.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Stomata are pores that open to let CO₂ enter the leaf for photosynthesis and to allow O₂ and water vapour to leave, enabling gas exchange.
The waxy cuticle coats the leaf surface and reduces evaporation, keeping water inside.
Together they balance the plant’s need to take in CO₂ while limiting water loss.
The waxy cuticle coats the leaf surface and reduces evaporation, keeping water inside.
Together they balance the plant’s need to take in CO₂ while limiting water loss.
Examiner tips
- Use the exact terms ‘stomata’, ‘CO₂’, ‘O₂’, ‘water vapour’, ‘waxy cuticle’, ‘evaporation’.
- Show the two functions (gas exchange and water conservation) in separate sentences.
Mark scheme (4 marks)
- Stomata allow carbon dioxide to enter the leaf (for photosynthesis)
- Stomata allow water vapour (and oxygen) to leave / allow gas exchange to occur
- The waxy cuticle reduces water loss from the leaf surface
- The two structures balance the need for gas exchange with the need to conserve water
Key terms in this question
Related
- All Eduqas GCSE Biology revision notes →
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- Decode the mark scheme abbreviations →