ASYNCHRONOUS RHYTHMS IN THE EMISSION OF VOLATILES FROM HESPERIS-MATRONALIS FLOWERS

Twelve monoterpenes and five aromatic compounds were identified from Hesperis matronalis flowers in situ. The most abundant compounds were 1,8-cineole, E-beta-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-beta-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 degrees than at 15 degrees, 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.