Which structure in plant leaves is responsible for gas exchange?

The structure in plant leaves responsible for gas exchange is the stomata. Stomata are small openings found on the surface of leaves that allow gases such as carbon dioxide, oxygen, and water vapor to enter and exit the leaf. During photosynthesis, plants take in carbon dioxide through these openings, which is essential for producing glucose and releasing oxygen as a byproduct. The regulation of these openings is crucial for maintaining the balance of gases in the leaf and preventing excessive water loss.

The cuticle serves as a protective layer that helps reduce water loss but does not facilitate gas exchange. Chloroplasts are the organelles where photosynthesis occurs, but they do not allow for gas exchange directly. Phloem is the tissue responsible for transporting nutrients and sugars produced during photosynthesis throughout the plant, rather than for gas exchange. Thus, stomata are uniquely suited for the critical function of allowing gases to pass into and out of the leaf, making them the correct choice.