Comparative study on the gametophyte morphology and development of three paramo species of Jamesonia (Pteridaceae, Polypodiopsida)

Abstract

The sexual phase of three species of Jamesonia (J. imbricata, J. rotundifolia and J. scammaniae) has been studied, from spore germination to gametangia formation, with special attention to the morphological development of prothalli. This is the first work to deal with gametophytes of species in this genus. All three species have trilete, tetrahedrical spores that germinate following the Vittaria type. The developmental pattern of J. imbricata and J. rotundifolia is intermediate between the Adiantum and Ceratopteris types, as the initial mitotic activity is assumed by an obconical apical cell, substituted later by a lateral meristem. In J. scammaniae, no apical cell or lateral meristem is formed, so the prothalli remain ameristic throughout the developmental process. Adult gametophytes are naked and variable in shape, in the same species ranging from typical cordate prothalli to irregularly lobed forms. Gametangia of normal shape and size was observed in both J. imbricata and J. rotundifolia, but not in J. scammaniae. Apogamy could be expected to occur in the genus, a phenomenon to be examined in the future. Comparisons are made with known species of related genera and results are discussed from an ecological perspective in the paramo environment.

Gametophytic phase of "Doryopteris triphylla" (Pteridaceae, Polypodiopsida).

“…This developmental pattern is one of the most widespread in the family, along with the Ceratopteris model (Atkinson & Stokey 1964, Nayar & Kaur 1969. However, in many ge-nera, an intermediate Adiantum-Ceratopteris way of development has been detected, in which an apical cell is formed but the meristem is lateral (Nayar & Bajpai 1964, Nayar & Kaur 1971, Gabriel y Galán & Migliaro 2011. It has been also stated that ameristic, irregular forms of development in these genera could be due to deviations from any of those Adiantum or Ceratopteris types, by means of inhibition of the initial meristematic cell (Gabriel y Galán & Migliaro 2011).…”

“…Gametophytic characters have long been evaluated in fern systematics (Atkinson & Stokey 1964, Nayar & Kaur 1971, Atkinson 1973. This fact continues to our days, particularly with the Pteridaceae, in which many studies focusing gametophytes are aimed to clarify the complex generic delimitation of the family (Rothfels et al 2008, Gabriel y Galán & Migliaro 2011, Sigel et al 2011, Gabriel y Galán & Prada 2012, Johnson et al 2012. In spite of all the effort made to describe gametophytes of ferns in general and the Pteridaceae in particular, the haploid phase of D. triphylla is not known yet, except for some works related to the spore (Tryon 1942, Tryon & Lugardon 1991.…”