Certified Forester Practice Exam

Which part of the leaf is responsible for gas exchange and water vapor release?

1. Upper epidermis

2. Palisade layer

3. Spongy layer

4. Lower epidermis

The correct answer is: Lower epidermis

The correct answer pertains to the lower epidermis, which contains stomata—the tiny openings that facilitate gas exchange between the internal leaf tissues and the atmosphere. Stomata allow for the intake of carbon dioxide needed for photosynthesis and the release of oxygen as a byproduct. Additionally, they play a crucial role in regulating water vapor release during transpiration. In contrast, other layers of the leaf serve different functions. The upper epidermis acts as a protective barrier, primarily preventing water loss and shielding the leaf from physical damage. The palisade layer, located just beneath the upper epidermis, is densely packed with chloroplasts and is primarily involved in photosynthesis. The spongy layer, situated below the palisade layer, has a loose structure that allows for gas exchange but is not directly responsible for it like the stomata in the lower epidermis. Thus, the lower epidermis is specifically adapted for the vital functions of gas exchange and water vapor release.