Solution:

Specialized cells known as guard cells surround stomata and function to open and close stomatal pores.

They also help to reduce water loss by closing when conditions are hot or dry.

Air enters the plant through these openings by gaseous diffusion and contains carbon dioxide which is used in photosynthesis and oxygen which is used in respiration.

Oxygen produced as a by-product of photosynthesis diffuses out to the atmosphere through these same openings.

Also, water vapor diffuses through the stomata into the atmosphere in a process called transpiration.