Does xylem develop before or after the root hairs?
The first xylem differentiation events occur in the elongation zone, well BEFORE the zone of maturation (where root hairs develop). In addition to water transport, xylem function is crucial to the maintenance of the acropetal (from shoot to root tip) flow of auxin. This in turn maintains the gradient of auxin in the root tip required for normal root function. While root hair development is a requirement for nutrient and water uptake, it is not as vital as the maintenance of the auxin gradient in the root tip.
