What major function do root hairs perform in a plant root?

• A. Increase surface area for water and mineral absorption from the soil.
• B. Absorb carbon dioxide from the soil.
• C. Store starch for energy.
• D. Provide structural support to the root.

Answer: (A)

Root hairs increase the surface area of the root in contact with soil, which makes absorption of water and dissolved minerals more efficient. These tiny, single-cell extensions from the root epidermis sit in the zone of maturation and vastly expand the area through which the root can take up moisture. Water moves into the root by osmosis along a water potential gradient, while minerals are pulled in by transport proteins that drive active uptake, aided by the larger surface area for exchange. Absorbing carbon dioxide from the soil isn’t a function of root hairs—the plant takes in CO2 through the leaves for photosynthesis. Storing starch happens in other root tissues, not in root hairs, and the hairs aren’t meant for structural support—the root’s framework comes from deeper tissues rather than these extensions.