Fragrance composition of Dendrophylax lindenii (Orchidaceae) using a novel technique applied in situ

The ghost orchid, Dendrophylax lindenii (Lindley) Bentham ex Rolfe (Orchidaceae), is one of North America’s rarest and well-known orchids. Native to Cuba and SW Florida where it frequents shaded swamps as an epiphyte, the species has experienced steady decline. Little information exists on D. lindenii’s biology in situ, raising conservation concerns. During the summer of 2009 at an undisclosed population in Collier County, FL, a substantial number (ca. 13) of plants initiated anthesis offering a unique opportunity to study this species in situ. We report a new technique aimed at capturing floral headspace of D. lindenii in situ, and identified volatile compounds using gas chromatography mass spectrometry (GC/MS). All components of the floral scent were identified as terpenoids with the exception of methyl salicylate. The most abundant compound was the sesquiterpene (E,E)-α-farnesene (71%) followed by (E)-β-ocimene (9%) and methyl salicylate (8%). Other compounds were: linalool (5%), sabinene (4%), (E)-α-bergamotene (2%), α-pinene (1%), and 3-carene (1%). Interestingly, (E,E)-α-farnesene has previously been associated with pestiferous insects (e.g., Hemiptera). The other compounds are common floral scent constituents in other angiosperms suggesting that our in situ technique was effective. Volatile capture was, therefore, possible without imposing physical harm (e.g., inflorescence detachment) to this rare orchid.