A student in Guyana investigated gas exchange in cassava plants and found that more stomata were present on the lower leaf surface than the upper surface. Which of the following best explains this distribution?

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Question

A student in Guyana investigated gas exchange in cassava plants and found that more stomata were present on the lower leaf surface than the upper surface. Which of the following best explains this distribution?

Accepted Answer

The lower surface is protected from direct sunlight, reducing water loss — Award 1 mark for explaining that stomata on the lower surface reduce excessive transpiration. A is incorrect — light reception does not determine stomatal position. C is incorrect — guard cells can develop on either surface. D is incorrect — carbon dioxide diffuses from all directions in the air spaces.

Answer

The lower surface is protected from direct sunlight, reducing water loss

Answer

The upper surface receives more light for photosynthesis

Answer

Carbon dioxide is only available from below the leaf

Answer

Guard cells only develop on shaded surfaces

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