Zygostates alleniana [Orchidaceae: Epidendroideae: Cymbidieae: Oncidiinae] floral structure related to pollination

The genus Zygostates Lindl. [Orchidaceae] comprises about 20 species of small Neotropical epiphytic plants, represented in its southernmost limit by the species Z. alleniana. In this paper, we studied morphological and anatomical floral characteristics of this species related to pollination mechanism. We confirmed the presence of the unicellular trichomes on the base of the lip and side lobes secreting oil, constituting a trichomal elaiophore. The oil is deposited beneath the cuticle at the apex of the trichomes forming small blisters. The oil could represent a reward for the species Lophopedia nigrispinis, which would be a potential pollinator of Z. alleniana in a natural area within the geographic range of this plant species. Moreover, we prove that the reconfiguration of the pollinaruim is due to the dehydration of the walls cell. This reconfiguration could favor cross-pollination mechanism already described for other species of the family Orchidaceae. Finally, we discuss the floral characters present in Z. alleniana with closely related species.