Table 1.
Known VOCs inducing direct responses in plants and/or priming of defences upon biotic or abiotic stress
| Compound | Species | Exposure time | Induced responses in the receiver plants | Primed responses upon stress in the receiver plants | Refs |
|---|---|---|---|---|---|
| Aldehydes | |||||
| Acrolein | Arabidopsis thaliana | 3 h | Increases the expression of defensive genes similar to those expressed upon Pseudomonas syringae infection and induces the production of jasmonates | Alméras et al., 2003 | |
| Methacrolein | Nicotiana attenuata | 72 h | Enhances the production of trypsin proteinase inhibitors in response to subsequent herbivory by Manduca sexta caterpillars | Kessler et al., 2006 | |
| Nonanal | Phaseolus lunatus | 6h and 24 h | All concentrations and times tested reduce infection by the bacterial pathogen P. syringae | Girón-Calva et al., 2012 | |
| Benzenoids | |||||
| Benzothiadiazole | P. lunatus | Spraying | Increases expression of PR-2 gene and increases resistance to P. syringae | Yi et al., 2009 | |
| Indole | Camellia sinensis | 48 h | Directly induces salicylic acid (SA) production | Increases resistance to Ectropis obliqua larvae. Up-regulates genes involved in Ca2+ signalling and mitogen-activated protein kinase and increases the production of phytohormones after herbivory | Ye et al., 2021 |
| Oryza sativa | 12 h | Increases the accumulation of 12-oxophytodienoic acid and up-regulates LRR-RLKs gene expression | Increases the expression of early defence signalling genes and enhances jasmonic acid (JA) production upon herbivory. Decreases Spodoptera frugiperda larval growth and damage | Ye et al., 2019 | |
| Zea mays | 12 h | Increases abscisic acid (ABA) production | Increases ABA and jasmonic acid isoleucine production upon wounding and application of Spodoptera littoralis regurgitant | Erb et al., 2015 | |
| Z. mays | 16 h | Increases jasmonate production and volatile abundance, and induces defence gene expression after herbivory | Hu et al., 2019 | ||
| (+)-Menthofuran | Cucumis sativus | Perfusion | Induces Vm depolarization | Maffei et al., 2001 | |
| Methyl salicylate (MeSA) | P. lunatus | 6h and 24 h | Reduces P. syringae infection | Girón-Calva et al., 2012 | |
| Green leaf volatiles | |||||
| (E)-2-Hexenal | A. thaliana | 15–20 min | Rapidly promotes cytosolic calcium ([Ca2+]cyt) transients and induces superoxide production | Asai et al., 2009 | |
| A. thaliana | 24 h | Up-regulates defence-related genes | Increases plant resistance to the necrotrophic fungal pathogen Botrytis cinerea | Kishimoto et al., 2005 | |
| Lolium temulentum | 1–60 min | Activates mitogen-activated protein kinases | Dombrowski et al., 2018 | ||
| N. attenuata | 72 h | Enhances the production of trypsin proteinase inhibitors to subsequent M. sexta caterpillar feeding | Kessler et al., 2006 | ||
| Solanum lycopersicum | Perfusion | Induces Vm depolarization and increases [Ca2+]cyt | Zebelo et al., 2012 | ||
| (Z)-3-Hexenal | A. thaliana | 24 h | Up-regulates defence-related genes | Increases plant resistance to the necrotrophic fungal pathogen B. cinerea | Kishimoto et al., 2005 |
| S. lycopersicum | Perfusion | Induces Vm depolarization and increases [Ca2+]cyt | Zebelo et al., 2012 | ||
| Z. mays | 30 min | Increases JA production and quantities of VOCs emitted | Increases JA production and quantities of VOCs emitted after Spodoptera exigua regurgitant application | Engelberth et al., 2004 | |
| Z. mays | 3–48 h | Up-regulates defensive genes and increases MeSA emissions | Farag et al., 2005 | ||
| (E)-2-Hexenol | A. thaliana | 15–20 min | Promotes [Ca2+]cyt transients | Asai et al., 2009 | |
| L. temulentum | 1–60 min | Activates mitogen-activated protein kinases | Dombrowski et al., 2018 | ||
| (Z)-3-Hexenol(E)-3-Hexenol | L. temulentum | 1–60 min | Activates mitogen-activated protein kinases | Dombrowski et al., 2018 | |
| Z. mays | 30 min | Increases JA production and quantities of VOCs emitted | Increases JA production and quantities of VOCs emitted after S. exigua regurgitant application | Engelberth et al., 2004 | |
| Z. mays | 20–60 min | Up-regulates genes involved in transcriptional regulation and Ca2+ and lipid signalling | Engelberth et al., 2013 | ||
| Z. mays | 14 h | Increases the quantity of VOCs and induces emissions of VOCs associated with herbivory, such as (Z)-3-hexenyl acetate, (3E)-DMNT, and sesquiterpenes | Ruther and Kleier, 2005 | ||
| (Z)-3-Hexenyl acetate(E)-3-Hexenyl acetate | P. lunatus | 24 h | Increases the production of extrafloral nectar | Heil et al., 2008 | |
| Populus deltoides × nigra | 16 h | Induces higher concentrations of JA and linolenic acid upon feeding by Lymantria dispar larvae. Up-regulates the expression of direct defence-related genes, and induces stronger and quicker emissions of terpenes upon larvae feeding | Frost et al., 2008 | ||
| S. lycopersicum | Perfusion | Induces Vm depolarization and increases [Ca2+]cyt | Zebelo et al., 2012 | ||
| Triticum aestivum | 16 h | Increases H2O2 production and increases activity levels of ROS-scavenging enzymes. Lowers infection rate by the fungus Fusarium graminearum and necrotic lesions induced by the fungus | Ameye et al., 2015; Van Meulebroek et al., 2020 | ||
| Z. mays | 30 min | Increases JA production and the quantities of VOCs emitted | Increases JA production and quantities of VOCs emitted after S. exigua regurgitant application | Engelberth et al., 2004 | |
| Z. mays | 1.5–4 h | Increases the expression of cold-stress-related genes | Reduces damage after cold stress | Cofer et al., 2018 | |
| Z. mays | 24 h | Directly induces defence gene expression in the absence of herbivory | Increases jasmonate production and volatile abundance, and induces defence gene expression after herbivory | Hu et al., 2019 | |
| (E)-2-Hexenyl acetate5-Hexenyl acetate(Z)-3-Hexenyl isovalerate(Z)-3-Hexenyl butyrate | P. lunatus | 24 h | Increases the production of extrafloral nectar | Heil et al., 2008 | |
| Jasmonates | |||||
| Methyl jasmonate (MeJA) | Gossypium hirsutum | 16 h | Increase emissions of (Z)-3-hexenyl acetate, (E)-β-ocimene, linalool, (3E)-DMNT, (E,E)-α-farnesene, (E)-β-farnesene, and (E,E)-TMNT | Rodriguez-Saona et al., 2001 | |
| S. lycopersicum | 24 h | Induces proteinase inhibitor I and II proteins | Farmer and Ryan, 1990 | ||
| Z. mays | 3–24 h | Increases the expression of defensive genes | Farag et al., 2005 | ||
| Ketones | |||||
| (Z)-Jasmone | Z. mays | 24 h | Reduces susceptibility to the leafhopper Cicadulina storeyi | Increases emission of the sesquiterpenes (E)-(1R,9S)-caryophyllene, (E)-α-bergamotene, (E)-β-farnesene, and (E)-DMNT upon insect feeding | Oluwafemi et al., 2013 |
| (–)-Menthone | C. sativus | Perfusion | Induces Vm depolarization | Maffei et al., 2001 | |
| Methyl vinyl ketone | A. thaliana | 3 h | Increases the expression of defensive genes upon P. syringae infection | Alméras et al., 2003 | |
| (+)-Pulegone | C. sativus | Perfusion | Induces Vm depolarization | Maffei et al., 2001 | |
| Vinyl ketone | A. thaliana | 3 h | Increases the expression of defensive genes upon P. syringae infection | Alméras et al., 2003 | |
| Terpenes | |||||
| Isoprene | A. thaliana | 72 h | Functions through SA signalling to prime plant defence and reduce the growth of the biotrophic pathogen P. syringae | Frank et al., 2021 | |
| α-Pinene | A. thaliana | 2 h | Increases pinII-promoter activity | Godard et al., 2008 | |
| A. thaliana | 15–20 min | Promotes [Ca2+]cyt transients | Asai et al., 2009 | ||
| A. thaliana | 72 h | Induces the accumulation of reactive oxygen species (ROS), and the expression of salicylic acid (SA)-and systemic acquired resistance (SAR)-associated genes | Riedlmeier et al., 2017 | ||
| S. lycopersicum | Perfusion | Induces Vm depolarization | Zebelo et al., 2012 | ||
| β-Pinene | A. thaliana | 72 h | Induces the accumulation of ROS, and the expression of SA-and SAR-associated genes | Riedlmeier et al., 2017 | |
| A. thaliana | 15–20 min | Promotes [Ca2+]cyt transients | Asai et al., 2009 | ||
| Cumene | Brassica nigra | 5 d | Reduces larval biomass | Pashalidou et al., 2020 | |
| Myrcene | A. thaliana | 2 h | Increases pinII-promoter activity and up-regulates genes associated with response to biotic or abiotic stress, defence, and transcription factors | Godard et al., 2008 | |
| A. thaliana | 15–20 min | Promotes [Ca2+]cyt transients | Asai et al., 2009 | ||
| Limonene | A. thaliana | 2 h | Increases pinII-promoter activity | Godard et al., 2008 | |
| 1,8-Cineole | A. thaliana | 2 h | Increases pinII-promoter activity | Godard et al., 2008 | |
| Artemisia tridentata | 24 h | Reduces herbivore damage | Shiojiri et al., 2015 | ||
| Linalool | A. thaliana | 2 h | Increases pinII-promoter activity | Godard et al., 2008 | |
| S. lycopersicum | 24h | Plants from the variety Moneymaker increased JA levels and expression of the PI-I gene 6 and 12 h after S. exigua caterpillar regurgitant treatment | Zhang et al., 2020 | ||
| (E)-β-Ocimene | A. thaliana | 15–20 min | Promotes [Ca2+]cyt transients | Asai et al., 2009 | |
| A. thaliana | 2 h | Increases pinII-promoter activity and up-regulates genes associated with response to biotic or abiotic stress, defence, and transcription factors | Godard et al., 2008 | ||
| Brassica pekinensis | 24 h | Increases the concentration of glucosinolates in leaves upon Myzus persicae infection and reduces the performance of M. persicae | Kang et al., 2018 | ||
| P. lunatus | 3–72 h | Up-regulates defence-related genes | Induces greater emissions of VOCs such as MeSA and (E)-DMNT after 1 d of feeding by Tetranychus urticae. Increases plant attraction to the predatory mite Phytoseiulus persimilis | Arimura et al., 2000a; Arimura et al., 2012, Muroi et al., 2011 | |
| S. lycopersicum | 24 h | Plants from the variety Moneymaker exposed to linalool showed increased expression of the PI-I and PI-II genes at 12 h after S. exigua caterpillar regurgitant treatment | Zhang et al., 2020 | ||
| S. lycopersicum | 72 h | Induces emissions of VOCs. Decreases susceptibility to Macrosiphum euphorbiae aphids and increases attractivity to Aphidius ervi parasitoids | Cascone et al., 2015 | ||
| Z. mays | 72 h | Induces greater emissions of VOCs after 1 d of feeding by Mythimna separata larvae and reduces larval weight gain | Muroi et al., 2011 | ||
| allo-Ocimene | A. thaliana | 24 h | Up-regulates defence-related genes | Increases plant resistance to the necrotrophic fungal pathogen B. cinerea | Kishimoto et al., 2005, 2006 |
| (E)-DMNT | A. thaliana | 15–20 min | Promotes [Ca2+]cyt transients | Asai et al., 2009 | |
| C. sinensis | 6 h | Decreases the amount of leaf eaten by Ectropis obliqua. Increases JA and SA contents and up-regulates defence-related genes | Jing et al., 2021 | ||
| Ipomoea batatas | 3 h | Increases trypsin inhibitory activity induced by Spodoptera litura feeding and reduces larval weight | Meents et al., 2019 | ||
| P. lunatus | 3h and 24 h | Increases the expression of defence-related genes | Arimura et al., 2000b | ||
| (E)-TMTT | P. lunatus | 24 h | Increases the expression of defence-related genes | Arimura et al., 2000b | |
| (–)-Menthol | C. sativus | Perfusion | Induces Vm depolarization and increases [Ca2+]cyt | Maffei and Camusso, 2001; Maffei et al., 2001 | |
| (+)-Neomenthol | C. sativus | Perfusion | Induces Vm depolarization | Maffei et al., 2001 | |
| (E)-Nerolidol | C. sinensis | 0.5–2 h | Activates mitogen-activated protein kinase, induces H2O2 burst, and increases JA and SA contents. Reduces susceptibility to the pathogen Colletotrichum fructicola | Increases resistance to Empoasca onukii | Chen et al., 2020 |
| β-Caryophyllene | S. lycopersicum | Perfusion | Induces Vm depolarization | Zebelo et al., 2012 | |
| A. tridentata | 24 h | Reduces herbivore damage | Shiojiri et al., 2015 | ||
| A. thaliana | 72 h | Functions through JA signalling to prime plant defence and reduce growth of the biotrophic pathogen P. syringae | Frank et al., 2021 | ||