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Abstract

Feeding by Pieris brassicae caterpillars on the lower leaves of Brussels sprouts (Brassica oleracea var. gemmifera) plants triggers the release of volatiles from upper leaves. The volatiles are attractive for a natural antagonist of the herbivore, the parasitoid Cotesia glomerata. Parasitoids are attracted only if additional damage is inflicted on the systemically induced upper leaves and only after at least three days of herbivore feeding on the lower leaves. Upon termination of caterpillar feeding, the systemic signal is emitted for a maximum of one more day. Systemic induction did not occur at low levels of herbivore infestation. Systemically induced leaves emitted green leaf volatiles, cyclic monoterpenoids, and sesquiterpenes. GC-MS profiles of systemically induced and herbivore-infested leaves did not differ for most compounds, although herbivore infested plants did emit higher amounts of green leaf volatiles. Emission of systemically induced volatiles in Brussels sprouts might function as an induced defense that is activated only when needed, i.e., at the time of caterpillar attack. This way, plants may adopt a flexible management of inducible defensive resources to minimize costs of defense and to maximize fitness in response to unpredictable herbivore attack.

Olfactory responses of Theocolax elegans (Hymenoptera, Pteromalidae) females to volatile signals derived from host habitats

“…There is considerable evidence that the volatile "alarm signals" are induced by interactions of substances from the herbivore with the damaged plant tissue (Steowe et al 1995). As demonstrated by Turlings et al (1991) for the parasitoid Cotesia marginiventris (Cresson) and its host Spodoptera exigua (Hübner) and by Mattiacci et al (2001) for Cotesia glomerata (L.) and its host Pieris brassicae (L.), plant volatiles can be induced by the saliva of caterpillars. Experienced L. distinguendus females have been shown to be strongly attracted to grains to which had been applied protein substances from original regurgitants (Tang et al 2013).…”

Induction of Defensive Responses in <i>Eucalyptus globulus</i> (Labill) Plants, against <i>Ctenarytaina eucalypti</i> (Maskell) (Hemiptera: Psyllidae)

“…These signals are transmitted in a systematic way to the whole plant [2]. They may be chemical (oligosaccharides, abscisic acid or sistemin) or physical (electrical signs) [3,4].…”

CHEMICAL DEFENSE RESPONSES IN Eucalyptus globulus (Labill) PLANTS

“…In both cases, the plants express a set of mechanical and physiological responses that could include, even as of the first incident, the activation of genes involved in defense 1,2 . When a biotic agent attacks a plant, it synthesizes and transmits signals systemically to the entire plant 3 . These signals may be chemical (synthesis of oligosaccharides, abscisic acid, and systemin) or electric 4,5 .…”