2.41 Explain how the structure of the leaf is adapted for gas exchange

• The cells in the spongy mesophyll (lower layer) are loosely packed, which increases the surface area of the leaf, allowing for more carbon dioxide to be absorbed
• Guard cells (stomata) on the lower part of the leaf controls the diffusion of gases in to the leaf.
• Leaves are thin, making it easier and quicker for gas to diffuse quickly through it.

Let me explain how the stomata work: 

- During the day, the guard cells are absorbing water (via osmosis), which makes them turgid, opening the stoma and therefore allowing gas into the plant

- At nighttime the opposite happens. The guard cells lose water, becoming flaccid and closing the stoma.