Asynchronous rhythms in the emission of volatiles from Hesperis matronalis flowers

Abstract Twelve monoterpenes and five aromatic compounds were identified from Hesperis matronalis flowers in situ . The most abundant compounds were 1,8-cineole, E - β -ocimene, linalool, and benzyl acetate. These four compounds were released asynchronously by the flowers during a photoperiod of 15 hr light and 9 hr darkness: 1,8-cineole was released mainly during the light period, E - β -ocimene mainly near the switch from light to darkness, and benzyl acetate mainly during the dark period. Linalool was not released rhythmically. Release rates of monoterpenes were higher at 20° than at 15°, while release rates of the aromatic compounds were not significantly different at these temperatures. The role of flower volatiles in host plant finding by a specialized Hesperis feeding weevil, Ceutorhynchus inaffectatus , is discussed.