Floral biology and histochemical analysis of Vanilla edwallii Hoehne (Orchidaceae: Vanilloideae): an orchid pollinated by Epicharis (Apidae: Centridini)

Abstract

The genus Vanilla is the most diverse in Vanilloideae, with ca 90 species distributed among tropical regions. Despite their economic importance, studies on pollination of Vanilla are very scarce and data on pollinators of species endemic to Brazil are lacking. Based on fieldwork and laboratory investigations, the floral biology of V. edwallii was studied. The pollinators and pollination process were recorded at the Serra do Japi reserve, state of São Paulo, southeastern Brazil, and the presence of floral reward was also investigated. Vanilla edwallii blooms in summer. The lateral inflorescences produce up to four pale green flowers. The white labellum is united to the base of the column forming a mentum. In the studied population V. edwallii is pollinated by Epicharis (Hoplepicharis) affinis, where the males exhibit a territorial behavior, defending flowers from other possible flower visitors. The pollen is deposited on the scutellum of bees when they abandon the flower. The mentum region is dry, suggesting no nectar production. The only secretory structures are osmophores dispersed on the inner surface of the lip responsible for production of a sweet fragrance, which together with color and morphology of flowers is related to bee attraction. The labellum is rich in mucilaginous cells, while the mucilaginous substance is retained inside the cells. The histochemical analysis also detected the presence of phenolic compounds and starch concentrated mainly at the adaxial surface of the lip and around the vascular bundles.

Microsatellite Markers Confirm Self‐Pollination and Autogamy in Wild Populations of Vanilla mexicana Mill. (syn. V. inodora) (Orchidaceae) in the Island of Guadeloupe

“…Spontaneous self-pollination is, therefore, an ancestral character in Vanilla shared by most, but not all, primitive species. Indeed, V. edwallii, from subgenus Vanilla, V. parviflora group, is not capable of self-pollination and requires a pollinator, supposedly the bee Epicharis (Hoplepicharis) affinis [32]. Autogamy in V. bicolor was explained by stigmatic fluids [28,31], and agamospermy was ruled out [31].…”

Osmophore structure and phylogeny ofCirrhaea(Orchidaceae, Stanhopeinae)

“…However, comprehensive data are available for, for example, species of Bulbophyllum (Teixeira et al ., ), Grobya amherstiae Lindl. (Pansarin et al ., ), C. dependens (Pansarin et al ., ) and Vanilla edwallii Hoehne (Pansarin, Aguiar & Pansarin, ). Davies & Stpiczyńska (, , , and ) also studied the anatomy of the secretory structures of Brazilian orchids, but with a greater focus on Oncidiinae and Maxillarinae.…”

“…(Curry et al, 1991), or have papillose and multicellular osmophores, such as Stanhopea lietzei (Regel) Schltr., S. insignis Frost ex Hook. (Pansarin, 2000;Pansarin & Amaral, 2009), S. tigrina (Curry et al, 1991), S. graveolens Lindl. and Cycnoches chlorochilon Klotzsch (Antón et al, 2012).…”

“…Stanhopea spp. appear as the most derived among Stanhopeinae and have hairy or papillose, multicellular osmophores (Curry et al, 1991;Pansarin, 2000;Pansarin & Amaral, 2009).…”

Taxonomic value of histochemical features of the style in early lineages of Asteraceae

“…Most studies developed in Asteraceae refer to either the recognition of secondary metabolites (e.g., Bohm & Stuessy 2001), the chemistry of the stigmatic surface in relation to the pollen-stigma interaction and the transmitting tissue of styles (e.g., Knox 1973;Hiscock 2000;Bessa et al 2010;Gotelli et al 2010), or the qualitative identification of organic compounds (proteins, carbohydrates, lipids) in medicinal plants or floral biology (Schorr & Costa 2003;Edeoga et al 2005;Korwar et al 2010;Nascimento-Silva et al 2011;Pansarin et al 2014). In this paper we examine lipophilic substances, tannins, proteins, reducing carbohydrates, starch, and oxalate in the styles of selected members of basal Asteraceae as an innovative approach to test if histochemical microanalysis techniques are a useful tool to complement classification studies.…”