Diverse labellar secretions in African Bulbophyllum (Orchidaceae: Bulbophyllinae) sections Ptiloglossum, Oreonastes and Megaclinium

摘要: Floral food-rewards of Bulbophyllum range from nectar to protein-rich mucilage and lipid-rich labellar secretions. For the first time, structure labellum secretory process are investigated for four African species. The most specialized type organization occurred in B. schinzianum, deep, narrow, median longitudinal groove consisting palisade-like cells flanked by trichomes containing lipid droplets, copious secretion sugar. This was absent or poorly defined, shallow wide, remaining taxa, scant lipid. All taxa possessed a striate cuticle lacking cracks pores, micro-channels were present, cuticular blisters occurring only B. schinzianum. contained storage parenchyma (B. lupulinum) mesophyll-like (B. schinzianum), but section Megaclinium (B. falcatum B. maximum), these replaced aerenchyma. In form groove, sweet fragrance sugary suggest pollination Hymenoptera, food-reward indicating that pseudocopulation is unlikely. Conversely, having smaller flowers, secretion, suggests small flies. aerenchyma may facilitate this even aid wind-assisted pollination. © 2015 Linnean Society London, Botanical Journal Society, 2015, ●●, ●●–●●.