Gases enter and exit the leaf primarily through tiny openings called stomata. These are small pores located mostly on the underside of the leaf. Stomata play a crucial role in the process of photosynthesis, allowing carbon dioxide to enter the leaf for the production of glucose while releasing oxygen as a byproduct.
Each stoma is surrounded by two specialized cells known as guard cells, which regulate the opening and closing of the stomata. When the plant has enough water, the guard cells swell and open the stomata, facilitating gas exchange. Conversely, during dry conditions, the guard cells will close the stomata to conserve water, limiting gas exchange.
In summary, gases enter through the stomata, influenced by the behavior of the guard cells in response to environmental conditions.