Thale cress root. Light micrograph (LM) of the root of a Thale cress plant, Arabidopsis thaliana. The root has many fine root hairs on it. Root hairs are tubular extensions from absorptive cells in the root. The hairs help to anchor the plant in the soil and enormously increase the root's absorptive surface area. The water and nutrients that root hairs absorb travel to the vascular centre of the root and then on to the rest of the plant. A. thaliana is used as an international plant standard for genetic research. This research is vital for improving our understanding of crop plants.