AOBPreview originally published online on November 3, 2006
Annals of Botany 2007 99(1):131-139; doi:10.1093/aob/mcl231
Floral Anatomy of Paepalanthoideae (Eriocaulaceae, Poales) and their Nectariferous Structures
Departamento de Botânica, Instituto de Biociências, Universidade Estadual PaulistaUNESP, C.P. 199, Rio Claro, SP 13506-900, Brazil
* For correspondence. E-mail mm_rosa{at}hotmail.com
Received: 29 June 2006 Returned for revision: 9 August 2006 Accepted: 7 September 2006 Published electronically: 3 November 2006
BACKGROUND AND AIMS: Eriocaulaceae (Poales) is currently divided in two subfamilies: Eriocauloideae, which comprises two genera and Paepalanthoideae, with nine genera. The floral anatomy of Actinocephalus polyanthus, Leiothrix fluitans, Paepalanthus chlorocephalus, P. flaccidus and Rondonanthus roraimae was studied here. The flowers of these species of Paepalanthoideae are unisexual, and form capitulum-type inflorescences. Staminate and pistillate flowers are randomly distributed in the capitulum and develop centripetally. This work aims to establish a floral nomenclature for the Eriocaulaceae to provide more information about the taxonomy and phylogeny of the family.
METHODS: Light microscopy, scanning electron microscopy and chemical tests were used to investigate the floral structures.
KEY RESULTS: Staminate and pistillate flowers are trimerous (except in P. flaccidus, which presents dimerous flowers), and the perianth of all species is differentiated into sepals and petals. Staminate flowers present an androecium with scale-like staminodes (not in R. roraimae) and fertile stamens, and nectariferous pistillodes. Pistillate flowers present scale-like staminodes (except for R. roraimae, which presents elongated and vascularized staminodes), and a gynoecium with a hollow style, ramified in stigmatic and nectariferous portions.
CONCLUSIONS: The scale-like staminodes present in the species of Paepalanthoideae indicate a probable reduction of the outer whorl of stamens present in species of Eriocauloideae. Among the Paepalanthoideae genera, Rondonanthus, which is probably basal, shows vascularized staminodes in their pistillate flowers. The occurrence of nectariferous pistillodes in staminate flowers and that of nectariferous portions of the style in pistillate flowers of Paepalanthoideae are emphasized as nectariferous structures in Eriocaulaceae.
Key words: Eriocaulaceae, Paepalanthoideae, nectariferous structures, staminodes, staminate flowers, pistillate flowers, floral anatomy, monocotyledons, Poales