Abstract
A comparative anatomical study was carried out on the secretory structures of leaflets from taxa belonging to the genus Rhynchosia - taxa difficult to delimit because of uncertain interspecific relations - in order to evaluate the potential diagnostic value of these anatomical traits for taxonomic assignment. A further objective was to establish consensual denomination for these secretory structures. The new anatomical features found in these taxa were sufficiently consistent to separate the species evaluated. The presence and localization of glandular-punctate structures bulbous-based trichomes, the number of layers in the palisade parenchyma and the arrangement of vascular units distinguish the taxa investigated and these characteristics can be extended to other species of Papilionoideae. The trichomes analyzed were described and classified into five types. Depicted in diagrams, photomicrographs, and by scanning electron microscopy, and listed for the first time at the genus and species levels. The information obtained served to effectively distinguish the taxa investigated among species of Papilonoideae.
Highlights
Investigated in several studies, secretory structures have contributed to the taxonomy of Fabaceae at various taxonomic levels (Lackey 1978, Lersten and Curtis 1994, 1995, Teixeira et al 2000, FortunaPerez et al 2012)
Seen with the naked eye on leaflets of Rhynchosia Lour. (Fabaceae – Papilonoideae), these structures are regarded as important traits in anatomical investigations (Lackey 1978, Grear 1978), complementing and supporting infrageneric taxonomic studies
The outline of epidermal cells in all species is sinuous on the abaxial surface and irregular in the adaxial portion of the leaflet blade (Figs. 1 - 2)
Summary
Investigated in several studies, secretory structures have contributed to the taxonomy of Fabaceae at various taxonomic levels (Lackey 1978, Lersten and Curtis 1994, 1995, Teixeira et al 2000, FortunaPerez et al 2012). (Fabaceae – Papilonoideae), these structures are regarded as important traits in anatomical investigations (Lackey 1978, Grear 1978), complementing and supporting infrageneric taxonomic studies. Distributed in tropical and subtropical areas in both hemispheres, the genus Rhynchosia comprises 230 species (Grear 1978), grouped into two sections and six series: Copisma, comprising four series, and Arcyphyllum, with two (Grear 1978). Challenges circumscribing and identifying Rhynchosia species have been reported by Grear (1978), Fortunato (2000), and Rogalski and Miotto (2011)
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