Localization of XET activity in 6-d-old Arabidopsis roots using XXXG-SR. A, Wild-type Col-0. The inset (arrow) with detector attenuation highlights root hair initiation and root hair staining. B, xth31-1/xth32-1 double knockout, showing root hair initiation and elongation zone staining. C, xth31-1/xth32-1 double knockout, a second example showing root hair, root hair initiation, and elongation zone staining. Representative images from the analysis of approximately 10 plants from each line are shown. [See online article for color version of this figure.]