MICROFIBRILS, MICROTUBULES AND MICROFILAMENTS OF THE TRICHOBLAST OF EQUISETUM HYEMALE

SUMMARY The cell wall of the trichoblastic part of the root hair cell is helicoidal like the cell wall of the root hair proper. The rotation mode of the helicoid is counter‐clockwise and the angle between microfibrils in adjacent lamellae is approximately 40°. During trichoblast elongation cortical microtubules lie perpendicular to the axis of elongation. During root hair initiation and root hair growth cortical microtubules align according to the long axis of the forming hair, not in parallel with the microfibrils. The freeze‐substitution technique reveals microtubules in the apical dome of the forming hair, where they lie in random orientations enabling isodiametric expansion. Microtubules in these cells function in morphogenesis, but not in microfibril orientation. F‐actin cables, microfilaments, are present in the trichoblast; they form a network in the cell interior. They do not coalign with the microfibrils nor with the microtubules.