RESUMO
Resumen: En México, la familia Gleicheniaceae está representada por Dicranopteris flexuosa, Diplopterygium bancroftii, Gleichenella pectinata, Sticherus bifidus, S. brevipubis, S. palmatus y S. underwoodianus; existen pocos trabajos sobre el estudio de los gametofitos de algunas especies de esta familia, por lo que el objetivo es describir, comparar y aportar información sobre su germinación, desarrollo de los gametofitos y finalmente determinar si los caracteres de los prótalos son útiles en la delimitación taxonómica del grupo. Para ello se recolectaron ejemplares y esporas de cada taxón en el campo, las esporas se sembraron en cajas de Petri que contenían agar y medio nutritivo de Thompson, se cultivaron en germinadoras bajo condiciones controladas de luz (12hrs luz/oscuridad), humedad (50 %) y temperatura (18 °C noche y 25 °C día); se realizaron observaciones de material fresco y se tomaron fotomicrografías utilizando un microscopio óptico y un microscopio electrónico de barrido. Como resultado se distinguieron dos tipos de germinación Gleichenia y Cyathea. En cuanto al desarrollo protálico, se observaron tres tipos, Marattia, Osmunda y Drynaria. Debido a las variaciones en el tipo de germinación que no habían sido reportadas para la familia en la literatura, así como por la heterogeneidad presente en el patrón de desarrollo protálico y la presencia de más de cuatro células en los gametangios, es importante ampliar el estudio de otras especies para determinar el valor taxonómico de las características morfológicas de los gametofitos, así como para determinar si estas variaciones se presentan en otras especies de la familia.
Abstract: 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. Rev. Biol. Trop. 65 (3): 939-952. Epub 2017 September 01.
RESUMO
This study investigated the effects of different temperatures (25 and 30 ± 2 ºC), light levels (62, 42, 22 and 5 percent of natural light), and pH (4.0, 4.5, 5.0, 5.5, 6.0 and 6.7) on the spore germination of Gleichenella pectinata. To accomplish this, the spores were surface sterilized and sown in bottles containing mineral medium. The spores of G. pectinata are monolets and the perispore surface can show large and irregular deposits. During germination, filamentous gametophytes with and without developing rhizoids were observed. Only gametophytes which presented developed rhizoids were able to reach the heart-shaped developmental stage. Based on the collection, the rate of and gametophyte development were generally very low. The relative germination rates were higher at 25 ºC than at 30 °C. Moreover, the highest percentages of gametophytes with developed rhizoids were observed at 22 and 5 percent of natural light (8.8 ± 2.3 percent and 11.3 ± 2.2 percent respectively) and the highest percentage of heart-shaped gametophytes were observed at pH 4.5 and 5.0 (1.2 ± 0.8 percent and 2.2 ± 0.8 percent, respectively).
A finalidade deste estudo foi analisar o potencial germinativo dos esporos de G. pectinata e verificar os efeitos de níveis de luz (62, 42, 22 e 5 por cento da luz natural), das temperaturas de 25 e 30 ºC e de pHs entre 4,0 e 6,7 na germinação. Esporos de G. pectinata são monoletes e a superfície apresenta depósitos grandes e irregulares. Observamos três classes de desenvolvimento: esporos contendo cloroplastos, gametófitos filamentosos sem rizóides desenvolvidos e gametófitos filamentosos com rizóides desenvolvidos. Somente os gametófitos com rizóides desenvolvidos foram capazes de alcançar a fase cordiforme. As porcentagens de germinação foram mais elevadas à temperatura de 25ºC do que 30 ºC. As mais elevadas porcentagens de gametófitos com rizóides desenvolvidos foram observadas sob 22 e 5 por cento da luz natural e as porcentagens mais elevadas de gametófitos cordiformes foram observadas no pH 5,0.