Constitutive and herbivore-induced monoterpenes emitted by Populus x euroamericana leaves are key volatiles that orient Chrysomela populi beetles.
Chrysomela populi beetles feed on poplar leaves and extensively damage plantations. We investigated whether olfactory cues orientate landing and feeding. Young, unexpanded leaves of hybrid poplar emit constitutively a blend of monoterpenes, primarily (E)-beta-ocimene and linalool. This blend attracts inexperienced adults of C. populi that were not previously fed with poplar leaves. In mature leaves constitutively emitting isoprene, insect attack induces biosynthesis and emission of the same blend of monoterpenes, but in larger amount than in young leaves. The olfactometric test indicates that inexperienced beetles are more attracted by adult than by young attacked leaves, suggesting that attraction by induced monoterpenes is dose dependent. The blend does not attract adults that previously fed on poplar leaves. Insect-induced emission of monoterpenes peaks 4 d after the attack, and is also detected in non-attacked leaves. Induced monoterpene emission is associated in mature leaves with a larger decrease of isoprene emission. The reduction of isoprene emission is faster than photosynthesis reduction in attacked leaves, and also occurs in non-attacked leaves. Insect-induced monoterpenes are quickly and completely labelled by 13C. It is speculated that photosynthetic carbon preferentially allocated to constitutive isoprene in healthy leaves is in part diverted to induced monoterpenes after the insect attack.
Brilli
Federico
F
Istituto di Biologia Agroambientale e Forestale, Consiglio Nazionale delle Ricerche, Monterotondo Scalo, Rome, Italy.
Ciccioli
Paolo
P
Frattoni
Massimiliano
M
Prestininzi
Marco
M
Spanedda
Antonio Franco
AF
Loreto
Francesco
F
D000818:Animals; D002070:Butadienes; D001517:Coleoptera / Q000502:physiology*; D005247:Feeding Behavior; D045782:Hemiterpenes / Q000096:biosynthesis; D039821:Monoterpenes / Q000378:metabolism*; D010420:Pentanes; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism*; D032107:Populus / Q000378:metabolism*; D055549:Volatile Organic Compounds / Q000378:metabolism
D002070:Butadienes; D045782:Hemiterpenes; D039821:Monoterpenes; D010420:Pentanes; D055549:Volatile Organic Compounds; C005059:isoprene