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Rapid on-site screening of biogenic volatile emissions from leaves of living plants is demonstrated, using headspace solid-phase microextraction (HS-SPME) with a portable gas chromatograph (PGC), fitted with a low-thermal mass (LTM) column equipped with a miniature toroidal ion trap mass spectrometer (ITMS). For field sampling, the study was conducted at the Royal Botanical Garden, Cranbourne, Australia, with the sampling site located in the Peppermint Garden. Twelve designated plants in the families of Asteraceae, Lamiaceae, Myrtaceae, Pittosporaceae, and Rutaceae were chosen for this field study. A customised SPME syringe was used for headspace sampling and sample introduction; leaves were collected into vials, equilibrated, sampled onto a PDMS/DVB-coated fibre, then desorbed in the GC inlet in split mode. A resistively heated LTM, narrow bore (0.1 mm ID) non-polar capillary column heated at 2 °C s−1 to 270 °C, provided fast GC elution with total run time of 3 min. The miniaturised ITMS was operated over a mass range of 40–500 Da. This provided approximation of near-real-time measurement of leaf volatiles released from the plant. For a second study, PGC–ITMS is employed to profile essential oils from experimental hybrid and commercial Humulus lupulus L. (hop) plant extracts in the laboratory, and contrasted with bench-top data. Results were processed by chromatographic fingerprinting using retention times, and MS fragmentation pattern similarity criteria. Unsupervised multivariate analysis was performed to improve specificity for classification of different plant volatiles, yielding loading variables corresponding to chemical differences of the analysed plants. The combination of HS-SPME and portable GC–ITMS proved effective for rapid chemical expression of the plant volatile genotype in the field.

Pathogen attack and herbivore infestation have a major impact on plant health. In a model study, these two plant health issues were simulated to study whether plant health can be monitored at greenhouse scale through the analysis of volatile organic compounds (VOCs) in greenhouse atmosphere. To simulate pathogen attack and herbivore infestation, we repeatedly stroked the stems of tomato plants (Lycopersicon esculentum) and repeatedly removed their side shoots. In addition, we studied the effect of fruit picking on the concentration of plant-emitted VOCs in greenhouse atmosphere. Analysis of air samples obtained before these treatments revealed up to 17 VOCs that are known to be released from tomato plants, of which the most dominant one was the monoterpene ß-phellandrene. When plants were 7 weeks old, the concentration of this VOC was approximately 0.06 ppbv before treatment. When plants were 12 weeks old, this concentration was raised to approximately 0.14 ppbv. Stroking of the stems, removing the side shoots and fruit picking resulted in an increase in the concentrations of all mono- and most sesquiterpenes up to 60-fold, which was expected because these VOCs are well-known constituents of trichomes. The treatments did not result in substantially increased concentrations of the stress-related compounds ¿-copaene, methyl salicylate and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene. In contrast to stroking and fruit picking, shoot removal resulted in the emission of the lipoxygenase-derived product (Z)-3-hexenol in greenhouse atmosphere expressing cell membrane degradation. The findings presented in this paper focus on the feasibility of monitoring plant health through the analysis of VOCs in greenhouse air, but findings might also be relevant for atmospheric chemistry.

Tomato plants respond to herbivory by emitting volatile organic compounds (VOCs), which are released into the surrounding atmosphere. We analyzed the tomato herbivore-induced VOCs and tested the ability of tomato receiver plants to detect tomato donor volatiles by analyzing early responses, including plasma membrane potential (V(m)) variations and cytosolic calcium ([Ca²⁺](cyt)) fluxes. Receiver tomato plants responded within seconds to herbivore-induced VOCs with a strong V(m) depolarization, which was only partly recovered by fluxing receiver plants with clean air. Among emitted volatiles, we identified by GC-MS some green leaf volatiles (GLVs) such as (E)-2-hexenal, (Z)-3-hexenal, (Z)-3-hexenyl acetate, the monoterpene α-pinene, and the sesquiterpene β-caryophyllene. GLVs were found to exert the stronger V(m) depolarization, when compared to α-pinene and β-caryophyllene. Furthermore, V(m) depolarization was found to increase with increasing GLVs concentration. GLVs were also found to induce a strong [Ca²⁺](cyt) increase, particularly when (Z)-3-hexenyl acetate was tested both in solution and with a gas. On the other hand, α-pinene and β-caryophyllene, which also induced a significant V(m) depolarization with respect to controls, did not exert any significant effect on [Ca²⁺](cyt) homeostasis. Our results show for the first time that plant perception of volatile cues (especially GLVs) from the surrounding environment is mediated by early events, occurring within seconds and involving the alteration of the plasma membrane potential and the [Ca²⁺](cyt) flux.

The leaf volatile constituents of Isatis tinctoria L. (Brassicaceae) have been studied by Solid-Phase Microextraction and Gas chromatography/Mass Spectrometry (SPME/GC-MS). Seventy components were fully characterized by mass spectra, linear retention indices, and injection of standards; the average composition (ppm) as single components and classes of substances is reported. Aliphatic hydrocarbons, acids, alcohols, aldehydes and esters, aromatic aldehydes, esters and ethers, furans, isothiocyanates and thiocyanates, sulfurated compounds, nitriles, terpenes and sesquiterpenes were identified. Leaf volatiles in Isatis tinctoria L. were characterized by a high amount of isothiocyanates which accounted for about 40 % of the total volatile fraction. Isothiocyanates are important and characteristic flavour compounds in Brassica vegetables and the cancer chemo-protective attributes are recently responsible for their growing interest.

Previous work showed that anthocorid predators aggregate around gauze cages containing Psylla-infested trees in a pear orchard. Because anthocorids responded to odor from Psylla-infested leaves in a laboratory test, it was hypothesized that these aggregative responses in the field were triggered by olfaction of compounds associated with Psylla injury. We present chemical analyses of volatiles from damaged and undamaged plants and studies on behavioral responses of anthocorid predators to compounds released by damaged plants. Leaf headspace volatiles from clean and Psylla-infested pear trees were collected on Tenax and identified by GC-MS after thermodesorption. Twelve volatiles were found exclusively in headspace samples from Psylla-infested leaves. Six were present in significantly higher quantities in samples from infested leaves: the monoterpene, (E,E)-?-farnesene, the phenolic, methyl salicylate, and the green leaf compounds, (Z)-3-hexen-1-yl acetate, (Z)-3-hexen-1-ol, 1-hexyl-acetate, and 1-penten-3-ol. These compounds are known to be produced by plants, and damage by pear psyllids seems to trigger their emission. Blend composition varied and was partly correlated with tree or leaf age and degree of Psylla infestation. To study whether compounds associated with leaf injury elicit olfactory responses in anthocorid predators, apple-extracted (E,E)-?-farnesene, synthetic methyl salicylate, and (Z)-3-hexen-1-yl acetate were offered in a Y-tube olfactometer to field-collected adult Anthocoris spp. Significant positive responses were found to both the monoterpene and the phenolic, but not to the green leaf volatile. The results lend support to the hypothesis that predator attraction to herbivore-infested pear trees is mediated by herbivory-induced plant volatiles.