Gametophyte development in Mexican species of Gleicheniaceae
In Mexico, the Gleicheniaceae family is represented by different species such as Dicranopteris flexuosa, Diplopterygium bancroftii, Gleichenella pectinata, Sticherus bifidus, S. brevipubis, S. palmatus and S. underwoodianus. Currently, few studies have described the gametophytes of some species in this family, and our objective was to contribute to the knowledge, and to describe and compare different aspects of their germination, gametophyte development, and to determine if the prothallus characters are useful for taxonomic delimitations in the group. For this purpose, specimens and spores of each taxon were collected in the field, spores were sown in Petri dishes containing agar and Thompson nutrient medium, and grown in a plant growing chamber under controlled conditions of light (12 hr light/darkness), (50 %) humidity, and temperature (18 °C night, 25 °C day). Additionally, observations of fresh materials were made and photomicrographs were taken using both optical and scanning electron microscopes. Our observations allowed distinguishing two types of germination Gleichenia and Cyathea; and three types of prothallial development Marattia, Osmunda and Drynaria. Gametangia presented more than three cells, and this is considered a primitive feature by other authors. As some variations in the germination type were observed and have not previously been reported in the literature for this family, and because of the heterogenity in the patterns of the prothallial cell development, and gametangia of more than four cells, it is important to broaden the study to other species, in order to determine the taxonomic value of the morphological characters of the gametophyte, as well as to determine if these variations are present in other species of the family.