Fig. 5. When compared with wild-type root hairs (A), cap1 root hairs (B) are short, bulbous, and occasionally waved or branched (Bars, 200 µm). Growing wild-type hairs expressing GFP:FABD2 (C) have longitudinal actin cables within the proximal cytoplasm aligned with the axis of growth. F-actin forms a diffuse dynamic network at the growing distal end of the hair that regulates vesicle fusion to the tip. In cap1 growing hairs (D) the diffuse tip network is replaced by F-actin aggregates (brightly labelled by GFP:FABD2), which can be observed at the very tip of the hair. Bars, 20 µm. Long actin bundles are absent from the central regions of the cytoplasm and instead F-actin can be found in shorter accumulations restricted largely to the cell cortex. Imaging of the very tip of these growing root hairs shows the presence of GFP:fimbrin in bright aggregates at the cortex (F) in zones normally free of F-actin (E; bars, 5 µm).