Plants release water vapor through openings called what?

• A. Lenticels
• B. Xylem
• C. Guard cells
• D. Stomata

Answer: (C)

Water vapor exits through stomata, tiny openings on the surfaces of leaves (and some stems). Each stomatal pore is flanked by a pair of guard cells that regulate whether the pore is open or closed in response to factors like light, humidity, and the plant’s water status. When stomata are open, water vapor can escape in a process called transpiration, which also helps pull water up from the roots through the xylem. Lenticels are openings on woody stems for gas exchange in other tissues, and xylem is the tissue that transports water inside the plant; the openings themselves are stomata, controlled by the guard cells.