Volatiles from flowers of Nicotiana sylvestris, N. otophora and Malus × domestica: headspace components and day/night changes in their relative concentrations

Headspace components from the flowers of Nicotiana otophora and apple (Malus × domestica) were trapped on Tenax and identified by GC and GC-MS. Aromatic compounds from phenylpropanoid metabolism including benzyl alcohol were predominant as was shown earlier for Nicotiana sylvestris. Studies of diurnal emissions of identified volatiles from these species showed there was a marked increase (ca 10 fold) in aromatic compounds released from N. sylvestris inflorescences in situ at night compared to day. Marked diurnal changes in compounds from other biosynthetic pathways were not observed. Emissions of benzyl alcohol and other phenylpropanoid derived volatiles did not increase at night in inflorescences of N. otophora or flowering branches of apple, respectively. Aromatic compound emissions from N. sylvestris at 90 min intervals were determined over a 24 hr period using a purge and trap GC system for analyses. The aromatics were at relatively low levels after midday but subsequently increased to reach peak emissions around 2-3 a.m. followed by declines in these levels of emissions. Possible functions for the dark period enhanced emission of volatile aromatic compounds are discussed.