Figure 4.13 Young root tip with elongating root hairs. Root tip of Medicago truncatula showing the approximate zones of root elongation and differentiation relative to the tip. Root hairs are protuberances of epidermal cells that first emerge approximately 4 mm behind the root tip and elongate over the span of about two days until they are fully elongated in the differentiation zone of the root. (Photograph courtesy U. Mathesius)