M. Dicke et al., Jasmonic acid and herbivory differentially induce carnivore-attracting plant volatiles in lima bean plants, J CHEM ECOL, 25(8), 1999, pp. 1907-1922
Lima bean plants respond to feeding damage of two-spotted spider mites (Tet
ranychus urticae) with the emission of a complex blend of volatiles that ar
e products of several different biosynthetic pathways. These volatiles attr
act the carnivorous mite Phytoseiulus persimilis, a specialist predator of
the spider mites that exterminates entire prey populations, and thus the vo
latiles contribute indirectly to plant defense. The volatile blend constitu
tes information to the carnivores, and blend composition is an important fa
ctor in this. Jasmonic acid (JA) is involved in the signal transduction of
this induced defense. Application of JA through the petiole of Lima bean pl
ants induces a volatile blend that is similar, but not identical, to that e
mitted by spider mite-infested plants. The induced volatiles originate from
the lipoxygenase pathway, the shikimic acid pathway, and the isoprenoid pa
thway. Among the induced bean plant volatiles are nitriles and oximes. Of a
total of 61 components, 10 are emitted at significantly different rates. A
mong these are the terpene (E)-4,8-dimethyl-1,3,7-nonatriene and the phenol
ic methyl salicylate, two compounds that are known to attract P. persimilis
. A crucial test for comparing the effect of spider mite damage and JA appl
ication on volatile induction is the response of P. persimilis. The carnivo
re is attracted by volatiles from JA-treated plants. Moreover, even treatme
nt of Lima bean plants with methyl jasmonate vapor made the plants attracti
ve to the carnivorous mites. However, the predators prefer the volatiles fr
om spider-mite-infested Lima bean plants over those from JA-treated plants.
Thus, chemical as well as behavioral analyses demonstrate that spider mite
damage and JA treatment have similar, although not identical, effects on v
olatile induction in Lima bean plants.