The term transpiration refers to water loss from a plant through which structure?

• A. Stoma
• B. Chlorophyll
• C. Pistols
• D. Cambium

Answer: (A)

Transpiration is the loss of water vapor from a plant, and it occurs mainly through the stomata—tiny openings on the leaf surface that regulate gas exchange. When stomata are open, water vapor can diffuse out of the leaf as carbon dioxide comes in for photosynthesis and oxygen exits. This pore system is what drives most water loss because it directly connects the leaf interior to the atmosphere. Chlorophyll is the pigment involved in capturing light for photosynthesis, not a pathway for water escape. Pistils are reproductive parts of flowers, and cambium is a growth tissue that produces new vascular tissue—neither is a route for water loss. So, the structure responsible for transpiration is the stomata.