A root hair cell has a large surface area that is ideal for absorbing nutrients, and its sap has a higher salt concentration than the surrounding soil water. It has a semipermeable membrane that permits minerals and water molecules to enter but not to leave. Since it is responsible for providing nutrition and water to the plant, it possesses a tough wall that allows it to go deep underground.
A root hair cell is a very tiny extension of the root hair and is invisible to the unaided human eye. It grows from the tip of the root hair, has a diameter of between 10 to 17 micrometers and a length of 100 to 1500 micrometers. Its large surface area speeds up the absorption of water and nutrients through diffusion.
Root hair cells are continually formed at the tip of the root and stay alive for two to three weeks before dying. In legume plants, root hairs are involved in the formation of root nodules. After absorbing water and nutrients, the root hair cells pass these nutrients to the root of the plant for transportation to all its other parts. The root hair cell has five organelles, including the nucleus, plasma membrane, cytoplasm, vacuole and cell wall. It is protected by a strong wall, which also gives it its shape.