Which process describes movement of water through a plant from roots to leaves?

• A. Photosynthesis
• B. Transpiration
• C. Respiration
• D. Condensation

Answer: (B)

Water moving from roots to leaves happens through the transpiration stream in the plant’s xylem. As water exits the leaves via stomata during transpiration, negative pressure is created that pulls more water up from the roots. Cohesion between water molecules and adhesion to the walls of the xylem help maintain a continuous column, so the water can rise against gravity. This is a passive process—driven by evaporation at the leaves rather than by the plant using energy. Root uptake and mineral transport support the initial entry of water, and root pressure can assist a bit, but the upward movement from roots to leaves is best described by transpiration. The other processes involve different functions: photosynthesis uses water to make glucose but doesn’t describe the movement of water through the plant; respiration releases energy from stored sugars; condensation is a change of state outside the plant.