<P> Root hair cells are outgrowths at a tip of the plant's roots . Root hair cells vary between 15 and 17 micrometres in diameter, and 80 to 1,500 micrometres in length . They are found only in the zone of maturation, and not the zone of elongation, possibly because any root hairs that arise are sheared off as the root elongates and moves through the soil . Root hairs grow quickly, at least 1μm / min, making them particularly useful for research on cell expansion . </P> <P> Root hairs form an important surface as they are needed to absorb most of the water and nutrients needed for the plant . They are also directly involved in the formation of root nodules in legume plants . The root hairs curl around the bacteria which allows for the formation of an infection thread through into the dividing cortical cells to form the nodule . </P> <P> Having a large surface area, the active uptake of water and minerals through root hairs is highly efficient . Root hair cells also secrete acid (H from malic acid) which exchanges and helps solubilize the minerals into ionic form, making the ions easier to absorb . </P> <P> Root hair cells can survive for 2 to 3 weeks and then die off, at the same time new root hair cells are continually being formed at the tip of the root . This way, the root hair coverage stays the same . When a new root hair cell grows, it excretes a poison so that the other cells in close proximity to it are unable to grow one of these hairs . This ensures equal and efficient distribution of the actual hairs on these cells . </P>

What is the structure and function of a root hair cell