What is the name of the process by which plants lose water through their leaves?

• A. Transpiration
• B. Respiration
• C. Photosynthesis
• D. Calvin Cycle

Answer: (A)

Water lost from leaves happens mainly through tiny openings called stomata, where water evaporates from the leaf surface into the air. This process is called transpiration. It’s a key part of how plants pull water up from the roots through the xylem, using the evaporation of water to create a pull that moves water and minerals upward. Stomata open to take in carbon dioxide for photosynthesis, and in the same moment water vapor escapes, driving transpiration.

Transpiration is different from respiration, which is the metabolic process that releases energy by breaking down sugars in cells, and from photosynthesis (including the Calvin cycle), which builds sugars from carbon dioxide and water using light. Those processes involve energy capture and sugar production, not the loss of water from leaves. The rate of transpiration depends on factors like humidity, temperature, airflow, and light, all of which influence how much water vapor escapes through the stomata.