What is transpiration?

• A. Water uptake from soil
• B. Gas exchange in roots
• C. Sugar transport from leaves to roots
• D. Water loss from plant surfaces (primarily leaves) through stomata, aiding nutrient transport and cooling

Answer: (D)

Transpiration is the loss of water vapor from a plant’s surfaces, primarily through the stomata on the leaves. When stomata are open to allow carbon dioxide in for photosynthesis, water vapor escapes. This evaporation creates a negative pull that draws water and dissolved minerals up from the roots through the xylem, moving nutrients through the plant in a flow known as the transpiration stream. The water loss also helps cool the leaf, preventing overheating. The other descriptions refer to different plant processes—water uptake from soil is how the plant acquires water, gas exchange in roots isn’t the main transpiration site, and sugar transport from leaves to roots is phloem transport, not transpiration.