Microsporogenesis and ultrastructure of pollen grains in the cocoa plant, Theobroma cacao (Malvaceae)
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| Autores: | , , , , |
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| Formato: | artículo original |
| Estado: | Versión publicada |
| Fecha de Publicación: | 2023 |
| Descripción: | Microsporogenesis and ultrastructure of pollen grains in Thebroma cacao (Malvacea). Introduction: Studies on the microsporogenesis of the chocolate plant are non-existent and little is known about the ultrastructure of the pollen grains. Objectives: the microsporogenesis process is described for the first time and in detail, highlighting ultrastructural aspects of the pollen grains in T. cocao. Methods: More than 30 flowers were processed for each floral development stages according to the protocols for embedding and sectioning in paraffin. The obtained sections were stained with Safranin-Alcian Blue, PAS-Amidoblack and Lacmoid. Additional samples were processed on resin and stained with toluidine blue and ultrathin sections were examined by transmission electron microscopy (TEM). For scanning electron microscopy (SEM) observation, the material was fixed and dehydrated in 2,2-dimethoxypropane, then critically dried and plated with gold. Results: Anthers differentiated by a cellular mass at the ends distal to the staminal filaments. During development, the anthers wall presents several cellular layers and at maturates time; they are reduced to the epidermis and the endothecium. Microspore mother cells divide by mitosis and then undergo meiosis to form tetrads. The tapetum is secretory and remains intact until pollen grains is released, later it degenerates. During sporodermis formation, the exine is first deposited and then the intine. The pollen grains are isopolar, spheroidal, small, tricolpate. The sporodermis is semi-tected, with reticulate ornamentation, heterobrochated reticulum with the muri without ornamentation. The orbicles are individual, smooth and of different sizes. The ultrastructure shows that the pollen grains are semi-tected, the ectexin formed by the tectum, columellae and the basal layer that constitutes the reticulate ornamentation and a very thin and compact endexin. Abundant pollenkitt on the tectum and between the columellae is observed. The intina is very thin, but it develops widely in the colpos areas, forming a compact internal intina and an unusual external intina with a columellated appearance. Conclusion: Anthers structure and development follows the known patterns of angiosperms. Simultaneous microsporogenesis and centripetal deposition of the sporodermis have been previously described for Malvaceae. Intine characters are novel for the Family. |
| País: | Portal de Revistas UCR |
| Institución: | Universidad de Costa Rica |
| Repositorio: | Portal de Revistas UCR |
| Lenguaje: | Inglés Español |
| OAI Identifier: | oai:portal.ucr.ac.cr:article/51101 |
| Acceso en línea: | https://revistas.ucr.ac.cr/index.php/rbt/article/view/51101 |
| Palabra clave: | Cocoa; Malvaceae; microspore; palynology; pollen ontogeny; sporodermis; tapetum. Cacao; esporodermis; Malvaceae; microspora; ontogenia del polen; palinología; tapete |