Estruturas secretoras em cipó-d'alho (Mansoa standleyi (Steyerm.) A. H. Gentry, Bignoniaceae): ocorrência e morfologia

Abstract

Species of Mansoa are called "cipó-d'alho" because of the smell of garlic that wafts from their vegetative and reproductive parts. Since data on the morphology and occurrence of their secretory structures are scarce and even absent for M. standleyi, the present work characterizes the distribution and morphology of such structures in the vegetative aerial axis of the latter. To do so, samples of the leaf blade and of nodal regions were fixed and examined using histological and scanning electron microscope techniques. Histochemical tests with appropriate controls were carried out on the secretory structures during the secretory phase. Fly and ant individuals that visit the species were sampled, preserved and identified by an entomologist. The secretory structures of the vegetative aerial axis of M. standleyi are peltate and patelliform glandular trichomes. All develop asynchronously and are present in the nodal regions and leaf blade, mainly in their youngest parts. Trichomes form a secretory complex in the nodal regions while they are scattered in the leaf blade. Histochemical analyses revealed that the cupulate and patelliform trichomes are extrafloral nectaries and that the peltate ones present an alkaloid fraction. The visitors of the nodal glands are ants Crematogaster (Formicidae) and Ectatomma brunea (Vespoidea, Formicidae) and flies Oxysarcodexia (Sarcophagidae, subfamily Utitidae [Ulidiidae]). The secretory structures of the vegetative aerial axis of Mansoa standleyi are similar to those reported for Bignoniaceae. An extrafloral nectary is described for M. standleyi for the first time.