Novelties in the secretory structures of three species of Gongora (Orchidaceae: Stanhopeinae)

The members of the Stanhopeinae (Orchidaceae) bear osmophores, which are related to pollination since they exude volatile lipids that attract euglossine bees. Gongora spp. are pollinated exclusively by euglossine bees. In view of the structural diversity found in the flowers of this genus and the lack of data on other foraging insects that visit these flowers, we elucidated aspects of the anatomy of floral secreting structures in the Stanhopeinae group, focusing on structures in Gongora jauariensis, Gongora pleiochroma and Gongora minax, species from the Amazon Rainforest. Secretory structures were analysed using light, scanning and transmission electron microscopy, and histochemical and phytochemical procedures. Osmophores, extrafloral nectaries and elaiophores were observed. The three species bear a structured nectary on the bract and osmophores on both the sepals and labellum hypochile. In G. minax, the labellum (hypochile) shows chemical and structural characteristics of elaiophore and osmophores, suggesting that it has both functions. We report interactions between foraging ants and nectaries of Gongora spp. for the first time. Interactions with ants attracted by the nectaries on the bracts are beneficial for orchids, as the ants help to protect their reproductive structures.

Automated summary

This study investigated the floral secreting structures in Gongora species of the Stanhopeinae group, revealing the presence of osmophores, extrafloral nectaries, and elaiophores. Some species showed characteristics of both elaiophores and osmophores in their labellum, indicating dual functionality. Additionally, interactions with ants were observed, with ants attracted to the nectaries on the bracts aiding in protecting the orchids' reproductive structures.