Volatile monterpenes in Porophyllum gracile and P. ruderale (Asteraceae): identification, localization and insecticidal synergism with alpha-terthienyl
1998
Guillet, G. | Belanger, A. | Arnason, J.T.
Volatiles occurring in Porophyllum gracile and P. ruderale (Asteraceae) were identified in order to assess their role in integrated chemical defences against insects. Headspace and steam distillation techniques yielded a total of 12 mono- and sesquiterpenes and fatty acid derivatives. The glandular secretory cavities present on leaves of P. ruderale were large enough to permit direct sampling and were found to be particularly rich in volatile monoterpenes (73.6% of the integrated FID trace). Using reduction of relative growth rate of third instar Ostrinia nubilalis (Lepidoptera: Pyralidae) larvae as an index of insecticidal activity, the volatiles released from the secretory cavities located on the leaves of P. ruderale had no significant effect alone, but they synergized the effects of alpha-terthienyl, a toxic light-activated secondary compound also present in P. gracile and P. ruderale. This synergistic interaction was shown to be related to an enhanced accumulation of the alpha-terthienyl in O. nubilalis larvae when they were exposed to the volatiles emitted from the foliar secretory cavities of P. ruderale.
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