What are the openings on the underside of leaves that allow gases to pass through called?

The openings on the underside of leaves that allow gases such as carbon dioxide and oxygen to pass through are known as stomates, or stomata in plural. These structures are crucial for the process of photosynthesis and respiration in plants. Stomata enable the exchange of gases with the environment, allowing plants to take in carbon dioxide for photosynthesis and release oxygen as a byproduct. Additionally, they're involved in transpiration, the process by which water vapor is released from the plant into the atmosphere.

Chloroplasts are the organelles where photosynthesis takes place but do not function as openings for gas exchange. Xylem and phloem are types of vascular tissue in plants; xylem transports water and dissolved minerals from the roots to the stems and leaves, while phloem carries sugars and other metabolic products downward from the leaves. Thus, the role of stomates is unique and directly linked to gas exchange, which is essential for vital plant processes.