Root Hair Development

Root hairs are projections from the epidermal cells of the root that are thought to increase its effective surface area for nutrient and water uptake, enlarge the volume of exploited soil, and aid in anchoring the plant to the soil. Their formation occurs as a series of developmental processes starting with cell fate specification in the meristem. The root-hair-forming epidermal cell, or trichoblast, then participates in the diffuse growth phase associated with the elongation of the main root axis. After the fully elongated trichoblast exits the elongation zone, growth is reorganized and localized to the side in the process of root hair initiation. Initiation is then followed by a sustained phase of tip growth until the hair reaches its mature length. Thus, root hairs provide insight into a range of developmental processes from cell fate determination to growth control. The theme emerging from the molecular analysis of the control of root hair formation is that many regulators act at several stages of development. Root hair formation is also responsive to a multitude of nutrient and other environmental stimuli. Therefore, one explanation for the presence of the complex networks that regulate root hair morphogenesis may lie in the need to coordinate their highly plastic developmental program and entrain it to the current soil microenvironment being explored by the root.