... area to volume ratio. These small leaves have hairs or spines which trap layers of air which is rich in water vapour. This reduces the chances of wind moving the moist air layer away from the xerophyte plant. The trapped layer of air increases the thickness of the boundary layer which in turn reduces the rate at which water vapour can diffuse from the leaf into the air. This is also achieved by the stomata which have been sunk into pits or grooves or depressions in the leaf surface. The spines and hairs on the xerophytes also put off animals and humans from preying on them. Stomata in xerophytes do not open during the day so the question of how do they photosynthesise can be asked. Xerophytes obtain carbon dioxide through a process called crassulacean acid metabolism. This is where epidermal cells combine carbon dioxide collected at night with an ...

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