Anatomical analyses of floral and extrafloral secreting structures indicate the presence of nectaries and colleters in Stanhopea grandiflora Lindl.

Abstract

Anatomical studies involving secreting structures in Stanhopeinae have described lipid-producing structures, the osmophores, these structures have been linked to pollinator attraction. Stanhopea, which belongs to the subtribe Stanhopeinae, has Neotropical distribution and is exclusively pollinated by male Euglossini bees, which are attracted to the aromatic compounds exuded by osmophores—a secreting structure that produces volatile lipids. However, due to the structural diversity found in this genus and the lack of data on which foragers visit these flowers, our aim is to elucidate floral anatomical aspects of the Stanhopeinae group, focusing on the secreting structures of Stanhopea grandiflora Lindl., an orchid that occurs in the Amazon region. Analyses were performed under bright-field microscopy and scanning electron microscopy. Osmophores, nectaries, idioblasts and glandular trichomes were the secreting structures observed in Stanhopea grandiflora. The osmophores are responsible for attracting and offering rewards the male Euglossini bees, which are their exclusive pollinators, while the nectaries offering nectar to the foragers Dolichoderus and Azteca ants which in turn offer protection against herbivores. Nectariferous stomata and glandular trichomes role similar to those of colleters are described in the first record of the subtribe Stanhopeinae.