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Background: Plants grow in multi-species communities rather than monocultures. Yet most studies on the emission of volatile organic compounds (VOCs) from plants in response to insect herbivore feeding focus on one plant species. Whether the presence and identity of neighboring plants or plant community attributes, such as plant species richness and plant species composition, affect the herbivore-induced VOC emission of a focal plant is poorly understood. Methods: We established experimental plant communities in pots in the greenhouse where the focal plant species, red clover (Trifolium pratense), was grown in monoculture, in a two species mixture together with Geranium pratense or Dactylis glomerata, or in a mixture of all three species. We measured VOC emission of the focal plant and the entire plant community, with and without herbivory of Spodoptera littoralis caterpillars caged on one red clover individual within the communities. Results: Herbivory increased VOC emission from red clover, and increasing plant species richness changed emissions of red clover and also from the entire plant community. Neighbor identity strongly affected red clover emission, with highest emission rates for plants growing together with D. glomerata. Conclusion: The results from this study indicate that the blend of VOCs perceived by host searching insects can be affected by plant-plant interactions. [ABSTRACT FROM AUTHOR]

Plant volatiles influence host selection of herbivorous insects. Since volatiles often vary in space and time, herbivores (especially polyphagous ones) may be able to use these compounds as cues to track variation in host plant quality based on their innate abilities and previous experience. We investigated the behavioral response of naïve (fed on artificial diet) and experienced (fed on poplar) gypsy moth ( Lymantria dispar) caterpillars, a polyphagous species, towards constitutive and herbivore-induced black poplar ( Populus nigra) volatiles at different stages of herbivore attack. In Y-tube olfactometer assays, both naïve and experienced caterpillars were attracted to constitutive volatiles and volatiles released after short-term herbivory (up to 6 hr). Naïve caterpillars also were attracted to volatiles released after longer-term herbivory (24-30 hr), but experienced caterpillars preferred the odor of undamaged foliage. A multivariate statistical analysis comparing the volatile emission of undamaged plants vs. plants after short and longer-term herbivory, suggested various compounds as being responsible for distinguishing between the odors of these plants. Ten compounds were selected for individual testing of caterpillar behavioral responses in a four-arm olfactometer. Naïve caterpillars spent more time in arms containing ( Z)-3-hexenol and ( Z)-3-hexenyl acetate than in solvent permeated arms, while avoiding benzyl cyanide and salicyl aldehyde. Experienced caterpillars avoided benzyl cyanide and preferred ( Z)-3-hexenyl acetate and the homoterpene ( E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) over solvent. Only responses to DMNT were significantly different when comparing experienced and naïve caterpillars. The results show that gypsy moth caterpillars display an innate behavioral response towards constitutive and herbivore-induced plant volatiles, but also that larval behavior is plastic and can be modulated by previous feeding experience. [ABSTRACT FROM AUTHOR]

Background: The role of herbivore-induced plant volatiles as signals mediating the attraction of herbivore enemies is a well-known phenomenon. Studies with short-lived herbaceous plant species have shown that various biotic and abiotic factors can strongly affect the quantity, composition and timing of volatile emission dynamics. However, there is little knowledge on how these factors influence the volatile emission of long-lived woody perennials. The aim of this study was to investigate the temporal dynamics of herbivore-induced volatile emission of black poplar (Populus nigra) through several day-night cycles following the onset of herbivory. We also determined the influence of different herbivore species, caterpillars of the gypsy moth (Lymantria dispar) and poplar hawkmoth (Laothoe populi), and different herbivore developmental stages on emission. Results: The emission dynamics of major groups of volatile compounds differed strikingly in response to the timing of herbivory and the day-night cycle. The emission of aldoximes, salicyl aldehyde, and to a lesser extent, green leaf volatiles began shortly after herbivore attack and ceased quickly after herbivore removal, irrespective of the day-night cycle. However, the emission of most terpenes showed a more delayed reaction to the start and end of herbivory, and emission was significantly greater during the day compared to the night. The identity of the caterpillar species caused only slight changes in emission, but variation in developmental stage had a strong impact on volatile emission with early instar L. dispar inducing more nitrogenous volatiles and terpenoids than late instar caterpillars of the same species. Conclusions: The results indicate that only a few of the many herbivore-induced black poplar volatiles are released in tight correlation with the timing of herbivory. These may represent the most reliable cues for herbivore enemies and, interestingly, have been shown in a recent study to be the best attractants for an herbivore enemy that parasitizes gypsy moth larvae feeding on black poplar. [ABSTRACT FROM AUTHOR]

Highlights: [•] We produced an aroma rich green tea LTPGT (low temperature processed green tea). [•] The odorant compounds of LTPGT were characterised by GC–MS/O and AEDA analyses. [•] Indole increased initially, peaking at 16h, then gradually decreased in LTPGT. [•] [15N]Anthranilic acid was converted to [15N]indole and [15N]OX-indoles in LTPGT. [Copyright &y& Elsevier]