Explain how an increase in wind speed increases the rate of transpiration in a plant.

Cambridge International IGCSE Biology (0610) — 8.3 Transpiration · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Wind removes water vapour from the leaf surface, lowering the humidity around the leaf. This reduces the concentration of water vapour outside the leaf, increasing the concentration gradient between the inside and outside of the leaf. The larger gradient causes water vapour to diffuse out of the stomata more rapidly, so the rate of transpiration increases.

Examiner tips

Use the word ‘wind’ and explain its effect on humidity; link lower humidity to a higher concentration gradient; state that diffusion rate rises; keep answer concise and use correct terminology.
Show the causal chain: wind → lower external vapour → higher gradient → faster diffusion → more transpiration.

Common mistakes

Failing to mention the reduction in external humidity; confusing transpiration with evaporation; using vague terms like ‘more water leaves the plant’ without explaining the gradient mechanism.

Mark scheme (4 marks)

Wind removes / blows away water vapour from the surface of the leaf
This decreases the concentration of water vapour outside the leaf / lowers humidity around the leaf
This increases the concentration gradient of water vapour between the inside and outside of the leaf
So water vapour diffuses out of the stomata faster / rate of diffusion of water vapour increases

Key terms in this question

transpiration