Guard cells are associated with which plant process?

• A. Gas Exchange.
• B. Evaporation of Water From the Plant.
• C. Transpiration.
• D. Guttation.

Answer: (B)

Guard cells regulate the openings of stomata, which are the passages between the leaf interior and the atmosphere. When stomata are open, carbon dioxide can enter for photosynthesis and oxygen can exit, so the guard cells are directly linked to gas exchange. Water loss via transpiration happens because stomata openings allow water vapor to escape, but the primary association of guard cells is with enabling gas exchange. Guttation occurs at leaf margins through hydathodes and is not controlled by these guard cells.