Root hairs are the microscopic, elongated outgrowths from the outer layer of cells of a plant’s root. Root hairs absorb nutrients and moisture from the soil. Also known as absorbent hairs, root hairs are the rhizoids of a vascular plant, and they are found on the epidermis of a plant root. Root hairs collect mineral nutrients and water from the soil and carry this solution to the rest of the plant.
Root hairs are invisible to the naked eye and are only found in mature regions of a root. Root cells do not carry out photosynthesis, so they do not have chloroplasts. In legume plants, root hairs help form root nodules. Root hair cells range from 80 to 1,500 micrometers in length and 15 to 17 micrometers in diameter.
Root hairs have large surface areas to aid in the absorption of minerals, known as active uptake, and the absorption of water, known as osmosis. Root hair cells solubilize minerals into ionic form by secreting acid. The lifespan of a root hair is two to three weeks, and new root hair cells continually form on the root. New root hair cells excrete poison that prevents other cells in close proximity from growing a root hair, thus ensuring efficient root hair distribution.