Spore development in red algae. A case study with Nemalion helminthoides (Nemaliales, Rhodophyta)
Ouriques, Luciane; Cristina Bouzon, Zenilda; Laurita,
published: Jul 1, 2005
ArtNo. ESP142015700007, Price: 29.00 €
Light and electron (TEM, SEM) microscope studies were carried out on carpospore release, attachment and germination in Nemalion helminthoides (Velley in With.) Batters. It was observed that carpospores are released without a cell wall and embedded in a mucilage sheath. This sheath allows the spore attachment. Many cored vesicles occur in the peripheral cytoplasm in this stage. After attachment, a microfibrillar cell wall is produced. The cored vesicles which disappear apparently play a role in the wall's production. Each carpospore presents a single chloroplast with a single central pyrenoid. Lobes of parallel thylakoids radiate from the region of the pyrenoid, giving the whole chloroplast a somewhat stellate appearance. The carpospores which are germinated immediately after are attached to the substratum. The beginning of spore germination is led by the formation of a vacuole at one of the poles; the other pole produces a germ tube. As the degree of vacuolation increases, the cell contents move towards this tube. The spore body is thus transformed into a hyaline vacuole. As the germination proceeds, the tubular cell becomes progressively divided by a transversal wall. In the next stages, the filament grows by creeping along the substrate towards the division, giving rise to a gametophytic phase.