Abstract
ABSTRACT Notothylas vitalii is an endemic Brazilian hornwort species, easily identifi ed by the absence of pseudoelaters and columella, and the presence of yellow spores. Plant material was collected in Recife, Brazil, and the spores were sown onto Knop’s medium, germinating after thirty days only with the presence of light. Germination occurred outside the exospore, and only after the walls had separated into three or four sections did a globose sporeling initiate its development. Following longitudinal and transversal divisions, the initial loose mass of cells became a thalloid gametophyte, subsequently developing into a rosette-like juvenile thallus with fl attened lobes. Additional information concerning sporeling types in key genera of hornworts, such as and FoliocerosPhymatoceros, will be crucial for inferring the possible ancestral type and the evolution of this trait among hornworts. Our study supports the necessity of supplementary studies on sporeling development, combined with morphological and phylogenetic investigations, to help elucidate the evolution of the Anthocerotophyta and their distribution patterns.
Highlights
The earliest developmental stages of different bryophyte species can provide important sources of phylogenetic and evolutionary information (Nehira 1983; Mishler 1986; Duckett et al 2004)
Sporeling development in the phylum Anthocerotophyta varies from either an initial globose or cylindrical protonema developing outside the exospore, typifying exosporous germination, as in Anthoceros, Notothylas, Phaeoceros, and Megaceros, among others (Campbell 1895; Mehra & Kachroo 1962; Renzaglia 1978; Nehira 1983; Wada et al 1984; Herguido & Ron 1989), to a multicellular protonema developing inside the exospore, as in the epiphyte Dendroceros (Schuette & Renzaglia 2010) and in Nothoceros renzagliensis (Villarreal et al 2012)
The spores of the phylogenetically related genera Notothylas and Phaeoceros germinate outside the exospore, and their protonema develop into compact masses composed of only a few cells (Menéndez 1988; Cargill et al 2005; Renzaglia et al 2008)
Summary
The earliest developmental stages of different bryophyte species can provide important sources of phylogenetic and evolutionary information (Nehira 1983; Mishler 1986; Duckett et al 2004). Sporeling development in the phylum Anthocerotophyta varies from either an initial globose or cylindrical protonema developing outside the exospore (spore wall), typifying exosporous germination, as in Anthoceros, Notothylas, Phaeoceros, and Megaceros, among others (Campbell 1895; Mehra & Kachroo 1962; Renzaglia 1978; Nehira 1983; Wada et al 1984; Herguido & Ron 1989), to a multicellular protonema developing inside the exospore (endosporous germination), as in the epiphyte Dendroceros (Schuette & Renzaglia 2010) and in Nothoceros renzagliensis (Villarreal et al 2012).
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