Morfología, caracterización y distribución geográfica de Blechnum cordatum (Blechnaceae-Pteridophyta).

Abstract

ABSTRACT. Morphology, characterization, and geographical distribution of Blechnum cordatum (Blechnaceae-Pteridophyta). Specimens of Blechnum cordatum from localities of its large geographical area were analized. The species grows in Mesoamerica, Antillas and South America, from Venezuela and Colombia to Bolivia, SE and centre of Brazil, Paraguay, Argentina, centre and S of Chile, and Juan Fernández Islands. Blechnum cordatum is a tolerant, not vulnerable species, with large sporophytes; erect, scaly rhizomes; dimorphic fronds with scaly stipes and axes; lanceolate sterile laminae with lanceolate to oblong, coriaceae, finely denticulate to serrate, superficially scaly and hairy, attached by costa (peciolulate) pinnae, with cuneate- truncate to subcordate or auriculate bases, and narrowly lanceolate fertile laminae with vegetative tissue of pinnae reduced to the portion which support the undulate to erose indusia and continuous coenosorus. Veins are free, simple, geminate and furcate, the latter ramdomly dividing at different distances from the costa, all ending in large, active hydathodes. Aerophores, located only at the base of pinnae, may be absent. Spores have a cristate-reticulate perispore with filiform, ramified processes, and a smooth to granulate exospore. Based on this study, a new description of Blechnum cordatum, and its taxonomy is presented, along with comments on affinities with other neotropical and paleotropical species of the genus.Key words. Blechnaceae, Blechnum cordatum, morphology, taxonomy, palynology, geographical distribution.RESUMEN. Morfología, caracterización y distribución geográfica de Blechnum cordatum (Blechnaceae-Pteridophyta). Blechnum cordatum fue estudiado en especímenes de numerosas localidades de su extensa área de distribución. Crece en Mesoamérica, Antillas, Sudamérica, desde Venezuela y Colombia a Bolivia, SE y centro de Brasil, Paraguay, Argentina, centro y S de Chile e islas de Juan Fernández. Es una especie poco vulnerable, tolerante, con esporófitos grandes, rizomas a oblongas con pinnas coriáceas, lanceolado-oblongas, finamente denticuladas a aserradas, superficialmente escamosas y pilosas, unidas al raquis por la costa (pecioluladas), con bases cuneado- truncadas a subcordadas o auriculadas y láminas fértiles estrechamente lanceoladas con el tejido vegetativo de las pinnas reducido a la porción de la lámina que lleva el cenosoro continuo e indusio ondulado a eroso. Las venas son simples, geminadas y bifurcadas al azar a distancias variables de la costa y terminan en grandes hidatodos activos, sobresalientes o más o menos planos. Los aeróforos, presentes sólo en la base de las pinnas, pueden faltar. Las esporas son monoletas, con perisporio crestado-reticulado que lleva procesos filiformes y exosporio subliso a granulado. La especie se describe e ilustra en detalle, se actualiza su taxonomía y se comentan sus afinidades con otras especies neotropicales y paleotropicales del género.Palabras clave. Blechnaceae, Blechnum cordatum, morfología, taxonomía, palinología, distribución geográfica.

Biometry of stomata in Blechnum species (Blechnaceae) with some taxonomic and ecological implications for the ferns

“…This could also mean that stomatal size is genetically fixed at a specific level, over a more or less broad range of variation between pinna areas, pinnae, fronds and individuals. According to previous studies on different genera of the Pteridophyta, stomatal size exhibits a very low variability: Rolleri (1977) first mentioned this fact in Huperzia saurura; Rolleri et al (2003) and Rolleri (2004) achieved same results in all genera of the Order Marattiales; similar conclusions were obtained by Prada et al (2008) for Blechnum cordatum, after studying specimens from all its geographical distribution and altitudinal range. Analysis of species of every genus allowed measuring a large sample and these authors considered that size of stomata can be considered a specific trait, yet their range of variation can be considered a generic one.…”

“…4A). Even using stomatal density, some authors have previously reported a more strong variation between species, as the case of Huperzia saurura (Rolleri 1977) and B. cordatum (Prada et al 2008).…”

Sporophyte morphology and gametophyte development of the fern Blechnum sprucei (Pteridophyta: Blechnaceae)

“…Hieron. (Prada et al 2008) and B. proliferum. (Prada and Rolleri unpublished data), which points to affinities of the species with these two and others of the so-called B. cordatum group (Oliveira Dittrich 2005).…”

“…Rolleri and Prada (2006b) suggested that some of the groups established by Tryon and Tryon (1982) in Blechnum are quite restrictive, and had been defined using fairly few characters. The B. lineatum group is clearly artificial, and encompasses a number of not well known species which should be analyzed before considering the mere existence of the group as currently defined (Prada et al 2008.…”

Especies arborescentes del género <i>Blechnum</i> (Blechnaceae: Pteridophyta)

“…El término arborescente se utiliza tal como se indica en Font Quer (1982) y en Lellinger (2002), y no implica la existencia de un hábito arbóreo, derivado de la actividad cambial, sino que hace referencia al rizoma erecto y robusto que generalmente presentan estas especies. Los vocablos relacionados con la epidermis han sido utilizados por los autores en trabajos pteridológicos previos, como Prada et al (2008) y Prada & Rolleri (2005) y la relacionada con los estomas se ha tomado de Prabhakar (2003).…”