Cytochemical, Structural and Ultrastructural Characterization of Tetrasporogenesis in Bostrychia radicans (Ceramiales, Rhodophyta) from the Mangroves of Itacorubi and Rio Ratones, Santa Catarina, Brazil

Abstract

Little is known about the morphology and location of macromolecules, especially proteins and carbohydrates, in vegetative and reproductive structures of mangrove species, including Bostrychia radicans. Therefore, to gain a better understanding of tetrasporogenesis in B. radicans, cytochemical, structural and ultrastructual analyses were performed. Thalli were collected from mangroves in Florianópolis, Santa Catarina, Brazil. Fertile branches were fixed and processed for light microscopy (LM), confocal microcopy and transmission electron microscopy (TEM) observations. The LM sections were stained with toluidine blue, periodic acid-Schiff and Coomassie brilliant blue. Tetrasporogenesis occurs in the pericentral cells of the terminal branches. This process is initially characterized by an increase in cell volume, resulting from the proliferation of organelles. The young tetrasporangia remain connected to the basal cell by pit connections. After a considerable increase in volume, the tetrasporocytes divide tetrahedrally, giving rise to haploid spores. During this process, there is an increasing production of starch grains, causing the organelles to group. As the organelles proliferate, the plasma membrane undergoes simultaneous invaginations toward the tetrasporangium center. The most conspicuous organelle throughout tetrasporogenesis was the Golgi complex. Polysaccharidic components are predominant in the tetrasporangium cell wall throughout tetrasporogenesis. Although protein components prevail in the cytoplasm of younger tetrasporangia, there is a predominance of reserve material with maturation. In the initial phase, there is an increase in the number of chloroplasts and a significant increment of Golgi bodies which contribute to the formation of the amorphous portion of the cell wall and possibly the biosynthesis of starch grains.