Ultrastructure, differentiation and cell wall texture of trichoblasts and root hairs of ceratopteris thalictroides (L.) brongn. (Parkeriaceae)

Abstract

Trichoblasts and root hairs of Ceratopteris thalictroides (L.) Brongn. were studied by different techniques to survey their morphological features. Trichoblasts could be identified at an early stage by an intra-vacuolar precipitate appearing during fixation. Special attention was paid to root-hair initiation. No structures or changes were observed that play a role in the initiation of papilla formation. When the papilla is formed, vesicles and periplasmic membranes can be observed which may play a role in the weakening of the cell wall during the papilla outgrowth. During root-hair growth, the nucleus of the trichoblast moves from the trichoblast to a subapical position in the root hair. The nuclei of all root cells contain 2 types of nuclear inclusions, one of which is proteinaceous. The cell wall of the Ceratopteris root hair has a helicoidal texture and because the cortical microtubules run longitudinally in the root hair, no correlation can be made between the directions of microtubules and microfibrils in these root hairs.