Biologia reprodutiva de Galendra blanchetii E.S. Rand (Orchidaceae, Catasetinae)

Abstract

Galeandra (Catasetinae) comprises 18 species, of which 14 occur in Brazil. Although widely distributed in the Neotropical region, no species in the genus has had its reproductive system studied. With this in mind, this study aimed to investigate the floral and reproductive biology of G. blanchetii E.S. Rand, an epiphytic orchid endemic to Brazil. Field observations were carried out in two populations in remaining areas of the Amazon Forest in Northeastern Brazil. Observations were made from March to July 2018 to 2023, totaling 715 hours. We also carried out monthly phenological monitoring and reproductive biology treatments, the treatments were: (i) emasculation, (ii) manual pollination, (iii) manual cross-pollination, (iv) spontaneous self-pollination, in addition to natural fruit formation, the seeds were evaluated through 1% tetrazolium. Floral resources were evaluated based on morphology and histochemical tests. Furthermore, we characterized the floral scent and evaluated its role in attracting pollinators. The flowering of G. blanchetii is annual, with the flowers opening in the morning. Experimental treatments have shown that it is self-compatible but requires biotic vectors to form fruits. Seed viability in manual and natural cross-pollination treatments (control) was significantly higher compared to self-pollinated flowers, which had more aborted seeds or no embryos. The floral perfume-producing gland (osmophore) was identified on the external and internal surface of the lip, with adaxial epidermis and unicellular trichomes with NADI-reactive content, indicating the production of terpenes. Although there is a calcar, the presence of nectar was not found. The majority of visits were made by Apidae bees. The only effective pollinators were male Euglossini (Euglossa securigera and E. chordata) and a Centridini (Epicharis sp.). The majority of the floral fragrance of G. blanchetii is made up of benzenoids, with methyl salicylate and methyl benzoate being the majority, representing 83.3% of the species' perfume. Our data reveal that G. blanchetii attracts its pollinators through a double mechanism that combines scent as a resource, and food deception, attracting both females and males of Euglossa in search of nectar. Although these males seek perfumes, simply brushing the labellum does not guarantee effective pollination, making it necessary for the bee to be deceived and enter the calcar in search of nectar, thus having contact with the pollinaria