Two representatives of section Lepidorhiza, previously sometimes considered conspecific, Bulbophyllum levanae and Bulbophyllum nymphopolitanum, demonstrated both similarities and differences in floral features. There were significant differences in the length of sepals and micromorphological features of the labellum. In both species, osmophores are located on the extended apices of sepals and possibly on petals. An abundance of proteins in tepals is probably associated with the unpleasant scent of the flowers, whereas the thin wax layers on the epidermis are probably involved in the maintenance of the brilliance of floral tepals, which strongly attracts flies. In all tepals of both species, we noted the presence of dihydroxyphenolic globules in the cytoplasm after staining with FeCl. Comparison with ultrastructure results revealed that they were associated with plastids containing plastoglobuli. The most remarkable feature was the presence of a prominent periplasmic space in the epidermal cells of both investigated species. Furthermore, in the labellum of B. levanae, the cuticle contained microchannels. The combination of periplasmic space and microchannels has not previously been recorded.

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This micromorphological, chemical and ultrastructural study is a continuation of research conducted on the section Lepidorhiza . The Bulbophyllum echinolabium flowers comprised features that characterize a sapromyophilous syndrome, having large, glistening parts that emit an intense scent of rotten meat. The secretory activity was described in the hypochile (nectary in longitudinal groove and in the prickles) and the epichile (putative osmophore). The ultrastructural studies revealed a dense cytoplasm in the epidermis and subepidermal tissue with large nuclei and numerous mitochondria, the profiles of SER and RER, and dictyosomes. Large amounts of heterogeneous residues of secreted material (possibly phenolic) were present on the cuticle surface, similar to the unusual prominent periplasmic space with flocculent secretory material. The chemical analysis (GC/MS) of the scent profile of lips comprised carbohydrates and their derivatives (29.55% of all compounds), amino acids (1.66%), lipids (8.04%) and other organic compounds (60.73%). A great number of identified compounds are Diptera attractants (mainly Milichiidae, Tephritidae, Drosophilidae, Muscidae, Sarcophagidae, Tachinidae). The examination of visual and olfactory features indicates correlation between colour of flowers and the type of olfactory mimicry, where a dark colour labellum emits strong smell of rotten waste.

Flowers of Bulbophyllum weberi and B. cumingii are characterized by fly-pollinated features. The secretory activity was described in dorsal sepals in both species (putative osmophores), petals in B. weberi (possible osmophores) and adaxial surface of lips in both species. In the cells of dorsal sepals and petals of B. weberi proteins, dihydroxyphenols, lipids and starch grains were detected, in lateral sepals—lipids. Whereas in dorsal sepal of B. cumingii only lipids and starch grains were noted, in lateral sepals—proteins and dihydroxyphenols and in petals—proteins and starch grains. The lips in both species differed histochemically and ultrastructurally. The epidermal cells of lip groove in B. weberi contained lipids, proteins, starch grains in cytoplasm, dihydroxyphenols in vacuoles and pectic acids/mucilage on surface. Whereas in B. cumingii—few lipids, starch grains, no proteins, no dihydroxyphenols and no mucilage were noted. Ultrastructurally, in B. weberi, the secretory material was present on surface and vesicles building into plasmalemma, while in B. cumingii—cell wall ingrowths and microchannels in cuticle. The osmiophilic irregular materials and globular, osmiophilic globules in B. weberi are probably tannin-like materials. For the first time, we described the cell wall ingrowths in Bulbophyllum species: in lip of B. cumingii and petals of B. weberi.

Floral morphological adaptations and composition of secretions aim to ensure reproductive success. Maxillariella is part of the largest subtribe of Orchidaceae, and Maxillariella spp. are important components of the orchid flora of the Neotropics. The aim of this paper was to provide a detailed study of the reproductive biology of three morphologically and geographically distinct species: M. sanguinea, M. variabilis and M. vulcanica. For many years, species in this group were considered rewardless, but several studies have revealed that lips of some species may secrete resins. However, most published research has mainly focused on investigating either micromorphology (SEM, TEM, histochemistry) or fragrance composition (GC–MS). In this study, we make the first attempt to investigate Maxillariella flowers in a more comparative manner by combining both aspects. In all investigated species we reported the presence of resins with lipids, sugars and/or proteins, suggesting a potential role as a food reward. Scant quantities of residues indicate that they are produced periodically in small quantities. Chemical analysis revealed significant differences between species, however, the presence of some compounds was constant. Cycloartenal and cycloartenol (main ingredients of resin and wax-like material in some Maxillariinae) were not been found.