Biology 9700 · AS & A Level · The gas exchange system

The gas exchange system — practice question

This photomicrograph illustrates several xerophytic adaptations in leaf tissue. Which row gives the correct functions of structures 1, 2 and 3?

  • Areduces the water vapour concentration gradient between the inside and outside of the leaf: 1, 2 and 3; reduces evaporation from the epidermis: 3 only; traps a layer of moist air: 2 only
  • Breduces the water vapour concentration gradient between the inside and outside of the leaf: 1 and 2 only; reduces evaporation from the epidermis: 1, 2 and 3; traps a layer of moist air: 1 and 2
  • Creduces the water vapour concentration gradient between the inside and outside of the leaf: 1 only; reduces evaporation from the epidermis: 2 and 3 only; traps a layer of moist air: 1 and 2
  • Dreduces the water vapour concentration gradient between the inside and outside of the leaf: 2 and 3 only; reduces evaporation from the epidermis: 1 and 2 only; traps a layer of moist air: 1 only

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