Which mineral transport system moves water upward from roots to leaves?

• A. Phloem via active transport
• B. Pericycle cells
• C. Epidermis
• D. Xylem via the cohesion-tension (transpiration pull) mechanism

Answer: (D)

The main idea here is how water gets pulled upward through the plant. Water moves up through the xylem by cohesion-tension, driven by transpiration in the leaves. When stomata open, water evaporates from the leaf surfaces, creating negative pressure (tension) in the xylem. Water molecules stick to each other (cohesion) and to the walls of the xylem (adhesion), so a continuous column of water can be pulled from the roots all the way to the leaves. The xylem’s structure—hollow, lignified vessels and tracheids—allows it to transport water under tension without collapsing. Root pressure can contribute a little at the root, but it isn’t the main driver for lifting water to the foliage. Phloem transports sugars and uses a different pressure-based mechanism, not primarily for lifting water upward, and pericycle or epidermis are root tissues, not the water-transport system.