Morfología del polen en especies de Canna (Cannaceae) y su implicancia sistemática

Pollen morphology in species of Canna (Cannaceae), and systematics implications. The morphology of pollen grains of eight taxa of Canna, C. ascendens, C. coccinea, C. compacta, C. glauca, C. indica, C. paniculata, C. variegatifolia and C. fuchsina, an unpublished new species, were studied using light and scanning electronic microscopes. We used the Wodehouse technique on samples of 20 grains per specimen to measure the intine with a light microscope; and the density of spines (in 400μm2 fields) with scanning electronic microscopy. Pollen grains are spherical, echinate, omniaperturate. The sporoderm presents a very thin exine covering a thicker intine. Corrugate micro-perforate, sub-reticulate, rugate, rugulate, striate to folded, micro-striate, micro-granulate, and smooth types of the external surface of the sporoderm were found. The spines consist of exine, partially to completely covered by tryphine. The two-layered intine is the thicker part of the wall. Echinate ornamentation is a generic character in Canna, but size, surface and color of pollen walls, and density and shape of spines, are diagnostic for species. Pollen morphology supports the view of C. indica and C. coccinea as different species. Canna fuchsina grows in wild, dense colonies, in humid riverside forests from Buenos Aires and Santa Fe Provinces, Argentina; its characters suggest relationships with a not well known group of taxa, some of them hybrids, such as C. x generalis. However, as these plants showed normal, well formed grains, close to those of C. coccinea, that germinate over the stigmatic surfaces in fresh flowers, we decided to include their pollen in this study. Rev. Biol. Trop. 58 (1): 63-79. Epub 2010 March 01.

Se estudió la morfología de los granos de polen de ocho táxones de Canna, C. ascendens, C. coccinea, C. compacta, C. glauca, C. indica, C. paniculata, C. variegatifolia y C. fuchsina, nueva especie aún no descrita, que fueron estudiadas usando microscopio de luz y microscopio electrónico de barrido. Nosotros utilizamos la técnica de Wodehouse en muestras de 20 granos por espécimen para medir la intina con el microscopio de luz; y la densidad de espinas (en campos de 400μm2) con el microscopio electrσnico de barrido. Los granos de polen son esfιricos, equinados y omniaberturados. El esporodermo presenta una exina muy delgada cubriendo una intina gruesa. La superficie del esporodermo puede ser corrugada, microperforada, sub-reticulada, rugada, rugulada, plegada-estriada, micro-estriada, microgranulada o lisa. Las espinas están formadas por exina, cubiertas total o parcialmente por trifina. La intina esta formada por dos capas, es la parte más gruesa de la pared. La ornamentación equinada es un rasgo genérico en Canna, pero el tamaño, la superficie y el color del polen, y la densidad y forma de las espinas, son rasgos diagnósticos de las especies. La morfología del polen apoya el tratamiento de C. coccinea y C. indica como especies diferentes. Canna fuchsina crece formando densas colonias silvestres en selvas ribereñas húmedas de las provincias de Buenos Aires y Santa Fe, Argentina; sus características sugieren relaciones no muy bien entendidas en el grupo de taxones, algunos son híbridos tales como C. x generalis. Sin embargo, estas plantas muestran granos normales, bien formados, cercanos a los de C. coccinea, que germinan sobre el estigma de flores frescas, nosotros decidimos incluir su polen en este estudio.

Reproductive studies in ipecac (Psychotria ipecacuanha (Brot. ) stockes; Rubiaceae): pollen development and morphology

The aim of this work was to carry out the reproductive studies on Brazilian accessions of ipecac, Psychotria ipecacuanha. It presented heterostyly, with brevistylous and longistylous flowers. The pollen development was observed from the sections of the anthers embedded in resin. Anther development was normal as usually observed in dicotyledones, displaying four layers: outer epidermis, endothecium, middle layer and inner tapetum. The pollen was bicellular and filled with starch at the microspore stage. Pollen morphology was studied using SEM, which showed pollen polymorphism within and between the two floral morphs. Five types of pollen with reticulate or perforate exine were identified. The characteristics showed that the sexual process was as important as the vegetative propagation for the reproduction of this species.

Foram realizados estudos reprodutivos em acessos brasileiros de poaia, Psychotria ipecacuanha. Poaia apresenta heterostilia, com flores brevistilas e longistilas. O desenvolvimento do pólen foi estudado em cortes de anteras embebidas em resina. O desenvolvimento da antera seguiu o padrão normal para as dicotiledôneas, a qual apresentou quatro camadas: epiderme, endotécio, camada média, e tapete, a mais interna. O pólen apresentou-se bicelular e preenchido com amido no estágio de micrósporo. A morfologia do pólen foi estudada utilizando-se MEV. Foi observado polimorfismo polínico dentro e entre as duas formas florais. Foram identificados cinco tipos de grãos de pólen, com exina reticulada ou perfurada. Em seu hábitat natural, sabe-se que essa espécie apresenta propagação por multiplicação vegetativa, mas as características estudadas demonstraram que o mecanismo sexuado é tão importante para a reprodução dessa espécie quanto à propagação vegetativa.