The stomata in plant cells can be found in the epidermis of leaves, stems and other parts of the plant involved in gas exchange. The pores inside the spongy layer of the plant leaf help aid in the exchange of gases between the leaf and its environment, and these pores eventually open up to the outside through the stomata.
Stomata are bordered on each side by specialized guard cells that regulate the size of the opening of the pore. Air and carbon dioxide enter into these pores and are used in the processes of photosynthesis and respiration. The byproduct of these processes is oxygen, which is diffused into the atmosphere through these same pores in a process called transpiration.
The number of stomata that are present on a plant and the size of the openings vary depending on the plant’s environment, including the amount of light and the average temperature. Most of the stomata can be found in the lower portion of the epidermis, but some can be found in the upper layer. The stomata in the upper layer also contain chloroplasts, which absorb sunlight and are used in conjunction with water and carbon dioxide to produce food for the plant using photosynthesis.