Which tissue transports water and minerals from the roots to the leaves?

• A. Phloem
• B. Xylem
• C. Cambium
• D. Phellogen

Answer: (B)

Water and mineral transport from roots to leaves is carried by xylem. This tissue is made up of hollow, tube-like cells (tracheids and vessel elements) that run from the roots up through the stems to the leaves. Water and dissolved minerals move upward mainly because transpiration in the leaves creates a pull that draws water through the plant, and the cohesive forces between water molecules along with adhesion to the xylem walls help maintain a continuous column against gravity. Minerals are taken up by the roots and loaded into the xylem with the water, so they travel upward with that flow. Xylem is dead at maturity, and its lignified walls provide the strength to withstand tension and keep the conduits open.

Phloem transports sugars and other organic nutrients, and can move in multiple directions depending on source and sink, not primarily water and minerals. Cambium and phellogen are growth tissues and do not function in water/mineral transport.