Root hairs develop from trichoblasts

A growing root hair of corn (Zea mays) as seen with light microscopy in a longitudinal section of the root. It can be clearly observed that the hair is an extension of a rhizodermal cell called a trichoblast (a cell in the rhizodermis giving rise to a root hair), and not a separate cellular structure. Root hairs dramatically increase the external surface area of the root and are the site of most absorption of water and solutes.

The trichoblast nucleus (stained red) is migrating into the root hair. Notice two atrichoblasts (rhizodermal cells not producing root hairs), and rows of root cortex cells.