Volatiles of the inflorescences of the Madeiran orchids, Goodyera macrophylla Lowe and Gennaria diphylla (Link) Parl. and their role in pollination

Goodyera macrophylla, considered a rare endemic, and Gennaria diphylla are two native terrestrial Orchidaceae species that can be found mainly in Madeiran Laurisilva. The volatile compounds contributing to the floral scent of these two Madeiran orchids were analysed and compared for the first time. The volatiles, isolated by distillation -extraction in a Likens-Nickersontype apparatus, and those extracted by headspace sorption, were analysed by GC and GC-MS. The main volatile components isolated by distillation -extraction were y-terpinene (13%) and n-nonanal (11%) in G. macrophylla and n-octacosane (19%) and n - heptacosane (13 %) in G. diphylla. The main volatile components isolated by headspace sorption were p-cymene (2 1%), ot-pinene (15%) and linalool (14%) in G. macrophylla and cis-arbusculone (28%) and lilac alcohol (26%) in G. diphylla. The importance of the volatiles in the pollination of these orchids is discussed.