The potential role of volatile organic compounds on the colonisation of deadwood by saproxylic beetles.

Plants respond to environmental stimuli via the release of volatile organic compounds (VOCs), and neighboring plants constantly monitor and respond to these VOCs with great sensitivity and discrimination. This sensing can trigger increased plant fitness and reduce future plant damage through the priming of their own defenses. The defense mechanism in neighboring plants can either be induced by activation of the regulatory or transcriptional machinery, or it can be delayed by the absorption and storage of VOCs for the generation of an appropriate response later. Despite much research, many key questions remain on the role of VOCs in interplant communication and plant fitness. Here we review recent research on the VOCs induced by biotic (i.e. insects and pathogens) and abiotic (i.e. cold, drought, and salt) stresses, and elucidate the biosynthesis of stress-induced VOCs in tea plants. Our focus is on the role of stress-induced VOCs in complex ecological environments. Particularly, the roles of VOCs under abiotic stress are highlighted. Finally, we discuss pertinent questions and future research directions for advancing our understanding of plant interactions via VOCs.

From plant resistance response to the discovery of antimicrobial compounds: The role of volatile organic compounds (VOCs) in grapevine downy mildew infection

Microorganisms in soil are known to be a source and a sink of volatile organic compounds (VOCs). The role of the microbial VOCs on soil ecosystem regulation has been increasingly demonstrated in the recent years. Nevertheless, little is known about the influence of the microbial soil community structure and diversity on VOC emissions. This novel study analyzed the effect of reduced microbial diversity in soil on VOC emissions. We found that reduced levels of microbial diversity in soil increased VOC emissions from soils, while the number of different VOCs emitted decreased. Furthermore, we found that Proteobacteria, Bacteroidetes and fungi phyla were positively correlated to VOC emissions, and other prokaryotic phyla were either negatively correlated or very slightly positively correlated to VOCs emissions. Our interpretation is that Proteobacteria, Bacteroidetes and fungi were VOC producers while the other prokaryotic phyla were consumers. Finally, we discussed the possible role of VOCs as mediators of microbial interactions in soil.

Why plants constitutively emit certain volatile organic compounds is a question that has attracted numerous researchers since the discovery of emissions. A number of hypotheses exist regarding the role of constitutive volatile organic compounds and many of these highlight the role of these compounds in enhancing plant tolerance to certain abiotic stresses. As practically any stress can modify constitutive emissions and also elicit production of novel compounds (induced emissions), this chapter provides a review of the hypotheses with particular foci on the key environmental stresses – heat and drought. Furthermore, we discuss how changes in the atmospheric CO2 concentration over past and future geologic epochs are likely to affect the role of volatile organic compounds as an adaptation to abiotic stresses.

Decay of date palm wood by white-rot and brown-rot fungi

Composition and emission of VOC from biogas produced by illegally managed waste landfills in Giugliano (Campania, Italy) and potential impact on the local population

Volatile organic compounds (VOCs) emitted by seeds serve as promising biomarkers for assessing seed vigor, viability, and deterioration during storage. This review synthesizes current knowledge on the types and chemical classes of VOCs released by seeds, factors affecting their emission, and methods for their collection and analysis. VOCs indicate seed aging, with increased emissions of alcohols, aldehydes, and ketones associated with deterioration processes like lipid peroxidation. Volatile organic compounds (VOCs) associated with seed deterioration include alcohols like ethanol, which can indicate fermentation, aldehydes such as hexanal, which is linked to lipid oxidation, and ketones like 2-heptanone, which can result from microbial activity and contribute to off-flavors and rancidity. The quantity and composition of VOCs correlate with the extent of seed deterioration, potentially offering a rapid, non-destructive alternative to traditional germination tests for evaluating seed quality. VOCs also mediate interactions between seeds and microorganisms, influencing germination and stress responses. Different research findings regarding volatile organic compounds (VOCs) in seeds indicate their potential as indicators of seed quality, which could lead to improved seed management strategies. By utilizing VOC profiling, farmers can make informed decisions on seed selection and treatment, ultimately enhancing crop yield and resilience in agricultural practices. While VOC analysis shows promise for integration into seed quality testing, challenges remain in standardizing protocols and identifying robust markers across different seed types, species and storage conditions. Advances in VOC research may ultimately lead to novel solutions for improving seed and crop productivity. Future research directions in VOC analysis for seed quality testing should focus on standardizing VOC profiles across diverse seed species, integrating VOC analysis with precision agriculture technologies, exploring environmental influences on VOC emissions, developing non-invasive testing methods, conducting longitudinal studies on seed storage, applying VOCs in breeding programs, and establishing links between VOC emissions and disease resistance.

Dead wood and saproxylic beetle assemblages in a semi-deciduous forest in Southern Benin

Volatile organic compounds (VOCs) emitted by plants play a critical role in the structure of the faunal communities that are associated with them. The aim of this work was to provide a detailed list of VOCs emitted by the oak species Quercus pyrenaica Willd. and to analyse the spatio-temporal variation in the emission rates of these compounds and in the diversity of saproxylic beetle assemblages associated with this tree species. VOCs sample collection was carried out by a dynamic flow-through enclosure technique with subsequent analysis by gas chromatography–mass spectrometry. Statistical differences in the emission rates of VOCs and in the diversity of saproxylic beetles were found between seasons. Temperature and relative humidity seemed to be related to these variations. Spatially, neither qualitative nor quantitative statistical differences in the emission of VOCs were found. Nevertheless, the results demonstrated a trend such that larger trees emitted VOCs with higher intensity and hosted a greater diversity of saproxylic beetles. Our hypothesis that beetles responded to certain blends of VOCs emitted at different rates by potential host tress and not so much to the absence or presence of a particular compound was reinforced by the absence of qualitative differences in the VOCs emitted by trees of different sizes. These results open a new field of study, and it will be necessary to become more involved with the subject to evaluate the real influence of these VOCs released by trees in saproxylic beetle assemblages.

ABSTRACTEffect of three wood-decaying fungi on decomposition of spruce wood was studied in solid-state cultivation conditions for a period of three months. Two white rot species (Trichaptum abietinum and Phlebia radiata) were challenged by a brown rot species (Fomitopsis pinicola) in varying combinations. Wood decomposition patterns as determined by mass loss, carbon to nitrogen ratio, accumulation of dissolved sugars and release of volatile organic compounds (VOCs) were observed to depend on both fungal combinations and growth time. Similar dependence of fungal species combination, either white or brown rot dominated, was observed for secreted enzyme activities on spruce wood. Fenton chemistry suggesting reduction of Fe3+ to Fe2+ was detected in the presence of F. pinicola, even in co-cultures, together with substantial degradation of wood carbohydrates and accumulation of oxalic acid. Significant correlation was perceived with two enzyme activity patterns (oxidoreductases produced by white rot fungi; hydrolytic enzymes produced by the brown rot fungus) and wood degradation efficiency. Moreover, emission of four signature VOCs clearly grouped the fungal combinations. Our results indicate that fungal decay type, either brown or white rot, determines the loss of wood mass and decomposition of polysaccharides as well as the pattern of VOCs released upon fungal growth on spruce wood.

<p indent=0mm>Ozone pollution is becoming increasingly serious in China, the accurate calculation of the volatile organic compounds (VOCs) contributions to ozone formation potential is the precondition for scientific and effective ozone control strategies. Maximum incremental reactivity (MIR) is an effective tool to evaluate VOCs’ reactivities, which may vary significantly because of different atmospheric conditions, VOCs compositions, and the relative abundances of VOCs and NO_{<italic>x</italic>}. Nevertheless, the most widely used MIR calculated by Carter based on 39 urban areas in the United States reflected the ozone formation potential of each VOCs species under atmospheric conditions in US. Whether their MIR values are appropriate under atmospheric conditions in China or not is still under discussion. In order to calculate the real contribution of VOCs to ozone formation, we firstly calculated the indigenized MIR values for Chinese megacities. Box model based on the second Regional Atmospheric Chemistry Mechanism (RACM2) was used to calculate the indigenized MIR for China. Observed data of four megacities (Beijing-Tianjin-Hebei, Yangtze River Delta, Pearl River Delta and Chengdu-Chongqing) which represent the typical atmospheric conditions in China were used as input parameters in calculation. We set two scenarios (Base scenarios and MIR scenarios) for MIR calculation, where Base scenarios were established by selecting the fourth highest ozone day during three years’ observed data, MIR scenarios were set by adjusting the NO_{<italic>x</italic>} availability to obtain the scenarios where ozone formation was most sensitive to VOCs. MIR values were calculated via the ratio of the change in ozone concentration due to the change in VOCs concentration divided by the change of VOCs concentrations in MIR scenarios. MIR_CHN (MIR values for four megacities) was obtained by averaging the normalized MIR values of all sites, with an uncertainty of 25%. Compared to the MIR calculated by Carter (MIR_USA in this study), our results showed a larger range values between the most active VOCs and the most inert VOCs. The MIR_CHN values of highly reactive VOCs (such as internal alkenes, butadiene, anthropogenic dienes, terminal alkenes, isoprene and o/m/p-xylene) were higher than MIR_USA values. Whereas MIR_CHN values of low reactive VOCs (HC5 and acetylene) were lower than MIR_USA values. Values of MIR_CHN and values of MIR_UAS were comparable for the moderate reactive VOCs. The differences between MIR_CHN and MIR_USA may be caused by differences in simulation time, reaction mechanism, and proportion of ozone precursors, NO_{<italic>x</italic>} availability, and VOCs compositions. Ozone formation potential of four megacities calculated by the MIR_CHN were much higher than that calculated by the MIR_USA, which meant that using MIR_USA may not only underestimate ozone formation potential, but also miss the key VOCs species in ozone formation in China. The key VOCs were isoprene, internal alkenes and m/p-xylene in ozone formation in China based on MIR_CHN calculation.

Long-term aerosol size distributions and the potential role of volatile organic compounds (VOCs) in new particle formation events in Shanghai

Tree species and elevation influence the assemblage composition of saproxylic beetles in subtropical forest of east China

Chemosignaling diversity in songbirds: Chromatographic profiling of preen oil volatiles in different species

Main conclusionVOC emissions increased with herbivore load, but this did not result in concomitant increases in resistance in neighbouring plants, suggesting that communication occurred independently of herbivore load in emitter plants.Herbivore-damaged plants emit volatile organic compounds (VOCs) that can alert neighbours and boost their resistance. While VOC-mediated plant communication has been shown to be herbivore-specific, we know little about its contingency on variation in herbivore load. To address this knowledge gap, we tested herbivore load effects on VOC-mediated communication between potato plants (Solanum tuberosum) using the generalist herbivore Spodoptera exigua. First, we tested whether herbivore load (three levels: undamaged control, low, and high load) affected total VOC emissions and composition. Second, we matched emitter and receiver plants and subjected emitters to the same herbivore load treatments. Finally, we performed a bioassay with S. exigua on receivers to test for induced resistance due to VOC-mediated communication. We found that herbivory significantly increased total VOC emissions relative to control plants, and that such increase was greater under high herbivore load. In contrast, we found no detectable effect of herbivory, regardless of the load, on VOC composition. The communication experiment showed that VOCs released by herbivore-induced emitters boosted resistance in receivers (i.e., lower leaf damage than receivers exposed to VOCs released by control emitters), but the magnitude of such effect was similar for both levels of emitter herbivore load. These findings suggest that changes in VOCs due to variation in herbivore load do not modify the outcomes of plant communication.