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Plants adapt to balance growth–defense tradeoffs in response to both biotic and abiotic stresses. Green leaf volatiles (GLVs) are released after biotic and abiotic stresses and function as damage-associated signals in plants. Although, GLVs enter plants primarily through stomata, the role of stomatal regulation on the kinetics of GLV uptake remains largely unknown. Here, we illustrate the effect of stomatal closure on the timing and magnitude of GLV uptake. We closed stomata by either exposing maize (Zea mays) plants to darkness or applying abscisic acid, a phytohormone that closes the stomata in light. Then, we exposed maize seedlings to (Z)-3-hexen-1-ol and compared its dynamic uptake under different stomatal conditions. Additionally, we used (E)-3-hexen-1-ol, an isomer of (Z)-3-hexen-1-ol not made by maize, to exclude the role of internal GLVs in our assays. We demonstrate that closed stomata effectively prevent GLV entry into exposed plants, even at high concentrations. Furthermore, our findings indicate that reduced GLV uptake impairs GLV-driven induction of biosynthesis of sesquiterpenes, a group of GLV-inducible secondary metabolites, with or without herbivory. These results elucidate how stomata regulate the perception of GLV signals, thereby dramatically changing the plant responses to herbivory, particularly under water stress or dark conditions. [ABSTRACT FROM AUTHOR]

The zoophytophagous mirid predator Nesidiocoris tenuis and the ectoparasitoid Stenomesius japonicus are important biological control agents for several agricultural pests including the invasive leafminer, Phthorimaea absoluta, a destructive pest of Solanaceous crops especially tomato in sub-Saharan Africa. However, little is known about how feeding by N. tenuis can influence the tritrophic interactions in the tomato plant. Here, we tested the hypothesis that N. tenuis phytophagy would influence the tritrophic olfactory interactions between the host plant tomato and pest, predator, and parasitoid. In olfactometer assays, P. absoluta females and N. tenuis adults were both attracted to constitutive volatiles released by the tomato plant. Whereas females of P. absoluta avoided volatiles released by N. tenuis-infested plants, S. japonicus females and N. tenuis adults were attracted to the induced volatiles. In coupled gas chromatography-electroantennographic detection (GC-EAD) recordings of intact and N. tenuis-infested plant volatiles, antennae of P. absoluta and S. japonicus females both detected eight components, whereas N. tenuis adults detected seven components which were identified by GC-mass spectrometry (GC-MS) as terpenes and green leaf volatiles (GLVs). Dose-response olfactometer bioassays revealed that the responses of P. absoluta, N. tenuis, and S. japonicus varied with the composition and concentration of blends and individual compounds tested from N tenuis-induced volatiles. Females of P. absoluta showed no preference for an eight-component blend formulated from the individual repellents including hexanal, (Z)-3-hexenyl butanoate, and δ-elemene identified in the volatiles. On the other hand, S. japonicus females were attracted to an eight-component blend including the attractants (E)-2-hexenal, (Z)-3-hexenol, methyl salicylate, β-phellandrene, and (E)-caryophyllene. Likewise, N. tenuis adults were attracted to a seven-component blend including the attractants β-phellandrene, δ-elemene, and (E)-caryophyllene identified in the volatiles. Our findings suggest that there is potential for the use of terpenes and GLVs to manage the insects in the tritrophic interaction. [ABSTRACT FROM AUTHOR]

Plants perceive the presence and defence status of their neighbours through light and volatile cues, but how plants integrate both stimuli is poorly understood. We investigated if and how low Red to Far red light (R:FR) ratios, indicative of shading or canopy closure, affect maize (Zea mays) responses to herbivore‐induced plant volatiles (HIPVs), including the green leaf volatile (Z)−3‐hexenyl acetate. We modulated light signalling and perception by using FR supplementation and a phyB1phyB2 mutant, and we determined volatile release as a response readout. To gain mechanistic insights, we examined expression of volatile biosynthesis genes, hormone accumulation, and photosynthesis. Exposure to a full blend of HIPVs or (Z)−3‐hexenyl acetate induced maize volatile release. Short‐term FR supplementation increased this response. In contrast, prolonged FR supplementation or constitutive phytochrome B inactivation in phyB1phyB2 plants showed the opposite response. Short‐term FR supplementation enhanced photosynthesis and stomatal conductance and (Z)−3‐hexenyl acetate‐induced JA‐Ile levels. We conclude that a FR‐enriched light environment can prompt maize plants to respond more strongly to HIPVs emitted by neighbours, which might be explained by changes in photosynthetic processes and phytochrome B signalling. Our findings reveal interactive responses to light and volatile cues with potentially important consequences for plant‐plant and plant‐herbivore interactions. Summary statement: A Far‐red enriched environment, indicative of vegetation shade, makes maize plants more sensitive to stress volatiles emitted by their neighbours and prompts them to release more volatiles themselves. This might be mediated by changes in phytochrome B signalling and Far‐Red effects on photosynthesis. [ABSTRACT FROM AUTHOR]

Green leaf volatiles (GLVs) are important signaling compounds that help to regulate plant defenses against pests and pathogens. Made through the hydroperoxide lyase (HPL) pathway, they are rapidly produced upon damage and can signal to other parts of the same plant or even plants nearby, where they can induce rapid defense responses directly or prime them against impending danger. In this primed state, plants can respond faster and/or stronger should pests or pathogens attack. However, while all proteins and genes involved in the biosynthesis of GLVs have been identified, little is still known about how the first two steps in the pathway, e.g., oxygenation by a lipoxygenase (LOX) and subsequent cleavage by HPL, are facilitated within the damaged tissue, resulting in the production of Z-3-hexenal (Z3al) as the first committed product of the pathway. Here, we provide evidence that several factors might be involved in the production of Z3al, including pH, Ca2+, and an environment that is highly hydrophobic. We present a model in which the extraordinary circumstances that are present at the site of Z3al production are considered, and shine new light on potential regulatory mechanisms. [ABSTRACT FROM AUTHOR]

To date, the role of green leaf volatiles (GLVs) has been mainly constrained to protecting plants against pests and pathogens. However, increasing evidence suggests that among the stresses that can significantly harm plants, GLVs can also provide significant protection against heat, cold, drought, light, and salinity stress. But while the molecular basis for this protection is still largely unknown, it seems obvious that a common theme in the way GLVs work is that most, if not all, of these stresses are associated with physical damage to the plants, which, in turn, is the major event responsible for the production of GLVs. Here, I summarize the current state of knowledge on GLVs and abiotic stresses and provide a model explaining the multifunctionality of these compounds. [ABSTRACT FROM AUTHOR]

Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), has a long association with maize (Zea mays mays L., Poaceae) and is among the crop's most significant pests worldwide. We contrasted the preference for and performance of FAW on three maize cultivars: the Mexican landrace Tuxpeño, the USA inbred B73 and B73‐lox10; B73‐lox10 is deficient in production of jasmonic acid (JA), green leaf volatiles (GLVs) and herbivore‐induced plant volatiles (HIPVs). Female oviposition and neonate colonization preferences were assessed in triple‐choice tests in greenhouse settings. Performance was assessed on the bases of larval, pupal and adult weights, larval and pupal development times, and adult longevity. We expected females to preferentially oviposit on plants on which their offspring performed best, and neonates to randomly colonize plants because they disperse aerially, presumably oriented solely by wind currents. Females preferred to oviposit on Tuxpeño plants, followed by B73‐lox10 and B73 plants, whereas their offspring performed best on B73‐lox10 and poorest on Tuxpeño. In contrast, neonates preferentially colonized plants on which they performed best, B73‐lox10, though initially and transiently they colonized plants on which they performed poorly, B73 and Tuxpeño. Altogether, our results showed that FAW females preferred to oviposit on maize plants on which their offspring's performance was poorest (Tuxpeño), and neonates preferentially colonized plants on which their own performance was best (B73‐lox10), though they initially colonized plants that were detrimental to their performance (Tuxpeño, B73). These results suggested that the ovipositional choices of FAW mothers are uncoupled from their offspring's performance, but newborn offspring rectified their mother's sub‐optimal host plant choice by colonizing plants that enhanced their own performance. Notably, these results also suggested that aerially dispersing (ballooning) FAW larvae do not colonize plants randomly, and that plant volatiles (GLVs, HIPVs) and JA may be relevant to host plant selection by ballooning larvae. [ABSTRACT FROM AUTHOR]

Simple Summary: Plants and their insect neighbors engage in a silent dialogue that is vital for ecological health, a phenomenon often invisible to the naked eye. Scientists have unveiled a fascinating aspect of this dialogue: plants communicate using a unique language of scents known as volatile organic compounds (VOCs). These aromatic messages serve as a defense system, recruiting allies in the form of beneficial insects or broadcasting alerts to fellow flora about impending threats such as pests. Our investigation delves into the mechanics of these aromatic signals across diverse habitats, from the dense canopies of forests to the cultivated expanses of farmlands. We discovered that these VOCs are not just background noise but are instrumental in maintaining ecological harmony. They hold the potential to revolutionize our approach to crop protection, offering eco-friendly alternatives to conventional pesticides. This research is groundbreaking, as it deciphers nature's olfactory code, paving the way for harnessing VOCs to foster environmental sustainability and food security. By mimicking the botanical strategies observed in plants, we can devise sustainable solutions to agricultural challenges, steering us towards a greener and more resilient future. Plants communicate with insects and other organisms through the release of volatile organic compounds (VOCs). Using Boolean operators, we retrieved 1093 articles from the Web of Science and Scopus databases, selecting 406 for detailed analysis, with approximately 50% focusing on herbivore-induced plant volatiles (HIPVs). This review examines the roles of VOCs in direct and indirect plant defense mechanisms and their influence on complex communication networks within ecosystems. Our research reveals significant functions of VOCs in four principal areas: activating insect antennae, attracting adult insects, attracting female insects, and attracting natural enemies. Terpenoids like α-pinene and β-myrcene significantly alter pest behavior by attracting natural enemies. β-ocimene and β-caryophyllene are crucial in regulating aboveground and belowground interactions. We emphasize the potential applications of VOCs in agriculture for developing novel pest control strategies and enhancing crop resilience. Additionally, we identify research gaps and propose new directions, stressing the importance of comparative studies across ecosystems and long-term observational research to better understand VOCs dynamics. In conclusion, we provide insights into the multifunctionality of VOCs in natural ecosystems, their potential for future research and applications, and their role in advancing sustainable agricultural and ecological practices, contributing to a deeper understanding of their mechanisms and ecological functions. [ABSTRACT FROM AUTHOR]

Simple Summary: Spodoptera frugiperda is a significant global agricultural pest, particularly fond of maize. In agroecosystems, the interactions among plants, phytophagous insects, and their natural enemies form a complex web at three trophic levels, with volatile compounds playing a pivotal role in these interactions. Phytophagous insects utilize plant volatiles as chemical cues to accurately identify and locate their hosts. Furthermore, herbivore-induced plant volatiles (HIPVs) act as critical chemical messengers and play an essential role in mediating interactions across the three trophic levels. These interactions include inducing defense mechanisms in neighboring plants, attracting natural enemies to help suppress pest populations, or directly producing repellent substances to deter pests. Oral secretions (OS) play a vital role in this interaction, acting as a critical signaling conduit that modulates plant responses. In this study, the major agricultural pest S. frugiperda was examined, with the GOX gene targeted as a molecular focus. The findings indicate that the GOX gene influences HIPV emission in maize, providing valuable insights into plant–insect interaction mechanisms and laying a foundation for innovative plant protection strategies. The intricate relationships between plants and insects are essential for understanding ecological dynamics. Among these interactions, HIPVs serve as a pivotal defense mechanism. Our findings reveal the highly conserved nature of the GOX gene within the Lepidoptera order, highly expressed in the salivary glands of S. frugiperda, and its role in mediating maize's defense responses. Notably, salivary GOX activity expression significantly decreases subsequent gene knockout. The presence of GOX in the saliva of S. frugiperda significantly modulates the emission of HIPVs during maize consumption. This research delineates that GOX selectively inhibits the emission of certain green leaf volatiles (GLVs) while concurrently enhancing the release of terpene volatiles. This study unveils a novel mechanism whereby S. frugiperda utilizes GOX proteins in OS to modulate volatile emissions from maize, offering fresh perspectives on the adaptive evolution of phytophagous insects and their interactions with their preferred host plants. [ABSTRACT FROM AUTHOR]

Green leaf volatiles (GLVs) are important in giving grape a fresh and green aroma. But the changes in GLVs during the phenological development of grapevines are not well known. This study analyzed the GLVs and transcription levels of associated biosynthetic genes in six grape species from the Loess Plateau region at five stages of maturation. Thirteen GLVs were detected, showing unique patterns for each grape type at various growth phases. The primary components in six grapes were (E)-2-hexenal, (E)-2-hexen-1-ol, and hexanal. With the exception of Cabernet Franc in 2019, the overall GLV contents of the six types generally increased during growth and development, peaking or stabilizing at harvest. And Sauvignon Blanc, Cabernet Gernischt, and Cabernet Sauvignon exhibited higher total contents among the varieties. PLS-DA analysis revealed 3-hexenal's high VIP scores across two years, underscoring its critical role in grape variety classification. Correlation analysis revealed a strong positive correlation between the levels of hexanal, 1-hexanol, (E)-2-hexen-1-ol, (Z)-3-hexenyl acetate, nonanal, and (E, E)-2,6-nonadienal and the expression of VvHPL and VvAAT genes in the LOX-HPL pathway. Specifically, VvHPL emerges as a potential candidate gene responsible for species–specific differences in GLV compounds. Comprehending the changing patterns in the biosynthesis and accumulation of GLVs offers viticulturists and enologists the opportunity to devise targeted strategies for improving the aromatic profile of grapes and wines. [ABSTRACT FROM AUTHOR]

Plants emit a range of volatile organic compounds (VOCs) as a way of interacting with their biotic and abiotic surroundings. These VOCs can have various ecological functions, such as attracting pollinators, repelling herbivores, or may be emitted in response to abiotic stress. For the present dataset, we used gas chromatography coupled ion mobility spectrometry (GC-IMS) to analyse the VOCs emitted by different plant species under controlled conditions. GC-IMS is a rapid and sensitive technique for gas phase analysis, that separates VOCs based on their retention time and drift time, resulting in characteristic heatmaps where the xy-position of a signal corresponds to compound identity, while signal intensity reflects its abundance.In this dataset, rapid analysis by GC-IMS was used to record emission pattern of 140 plant species from different taxonomic groups. This includes both floral volatiles and emission from leaves after induced damage. The data was pre-evaluated and listed in one table, containing information on the plant material used, as well as information on the respective emission patterns (including already identified compounds). Thus, this dataset provides a broad overview over plant VOC emissions. These can be used to either check the distribution of knowns substances, or the specific emissions of plants for functional, ecological or physiological studies or as the starting point for chemotaxonomic studies. The extraordinary ease with which these data can be generated – with the suitable set-up – lends itself to larger scale systematic or ecological studies across plant (or animal) groups and even ecosystems.

Green leaf volatiles (GLVs) are important signaling compounds that help to regulate plant defenses against pests and pathogens. Made through the hydroperoxide lyase (HPL) pathway, they are rapidly produced upon damage and can signal to other parts of the same plant or even plants nearby, where they can induce rapid defense responses directly or prime them against impending danger. In this primed state, plants can respond faster and/or stronger should pests or pathogens attack. However, while all proteins and genes involved in the biosynthesis of GLVs have been identified, little is still known about how the first two steps in the pathway, e.g., oxygenation by a lipoxygenase (LOX) and subsequent cleavage by HPL, are facilitated within the damaged tissue, resulting in the production of Z-3-hexenal (Z3al) as the first committed product of the pathway. Here, we provide evidence that several factors might be involved in the production of Z3al, including pH, Ca2+, and an environment that is highly hydrophobic. We present a model in which the extraordinary circumstances that are present at the site of Z3al production are considered, and shine new light on potential regulatory mechanisms.

To date, the role of green leaf volatiles (GLVs) has been mainly constrained to protecting plants against pests and pathogens. However, increasing evidence suggests that among the stresses that can significantly harm plants, GLVs can also provide significant protection against heat, cold, drought, light, and salinity stress. But while the molecular basis for this protection is still largely unknown, it seems obvious that a common theme in the way GLVs work is that most, if not all, of these stresses are associated with physical damage to the plants, which, in turn, is the major event responsible for the production of GLVs. Here, I summarize the current state of knowledge on GLVs and abiotic stresses and provide a model explaining the multifunctionality of these compounds.

Plants communicate with insects and other organisms through the release of volatile organic compounds (VOCs). Using Boolean operators, we retrieved 1093 articles from the Web of Science and Scopus databases, selecting 406 for detailed analysis, with approximately 50% focusing on herbivore-induced plant volatiles (HIPVs). This review examines the roles of VOCs in direct and indirect plant defense mechanisms and their influence on complex communication networks within ecosystems. Our research reveals significant functions of VOCs in four principal areas: activating insect antennae, attracting adult insects, attracting female insects, and attracting natural enemies. Terpenoids like α-pinene and β-myrcene significantly alter pest behavior by attracting natural enemies. β-ocimene and β-caryophyllene are crucial in regulating aboveground and belowground interactions. We emphasize the potential applications of VOCs in agriculture for developing novel pest control strategies and enhancing crop resilience. Additionally, we identify research gaps and propose new directions, stressing the importance of comparative studies across ecosystems and long-term observational research to better understand VOCs dynamics. In conclusion, we provide insights into the multifunctionality of VOCs in natural ecosystems, their potential for future research and applications, and their role in advancing sustainable agricultural and ecological practices, contributing to a deeper understanding of their mechanisms and ecological functions.

The intricate relationships between plants and insects are essential for understanding ecological dynamics. Among these interactions, HIPVs serve as a pivotal defense mechanism. Our findings reveal the highly conserved nature of the GOX gene within the Lepidoptera order, highly expressed in the salivary glands of S. frugiperda, and its role in mediating maize’s defense responses. Notably, salivary GOX activity expression significantly decreases subsequent gene knockout. The presence of GOX in the saliva of S. frugiperda significantly modulates the emission of HIPVs during maize consumption. This research delineates that GOX selectively inhibits the emission of certain green leaf volatiles (GLVs) while concurrently enhancing the release of terpene volatiles. This study unveils a novel mechanism whereby S. frugiperda utilizes GOX proteins in OS to modulate volatile emissions from maize, offering fresh perspectives on the adaptive evolution of phytophagous insects and their interactions with their preferred host plants.

Volatile organic compounds mediate plant-to-plant communication, and plants receiving volatile cues can acquire greater defenses against attackers. It has been expected that volatiles are received by factors that eventually lead to the induction of defense-related gene expression; however, the nature of these factors remain unclear. Structure-activity relationship analysis of gene expression induction by volatiles should provide insights into the nature of these factors. We conducted a structure-activity relationship study using maize seedlings and (Z)-3-hexen-1-yl acetate (Z3HAC) as the lead compound. The acid portion of Z3HAC was not essential, and (Z)-3-hexen-1-ol (Z3HOL), which is formed after the hydrolysis of Z3HAC, is likely the structure essential for the upregulation of the genes. The double bond of Z3HOL is essential; however, its geometry is indistinguishable. Strict specificity was detected regarding the length of the methylene chain on the α- and ω-sides of the double bond, and therefore, the 3-hexen-1-ol structure was found to be the ultimate structure. This finding provides insight into the nature of the factors that interact with a volatile compound and subsequently activate signaling pathways, leading to the upregulation of a subset of defense genes.

Green leaf volatiles (GLVs), volatile organic compounds released by plants upon tissue damage, are key signaling molecules in plant immunity. The ability of exogenous GLV application to trigger an induced resistance (IR) phenotype against arthropod pests has been widely reported, but its effectiveness against plant pathogens is less well understood. In this study, we combined mRNA sequencing-based transcriptomics and phytohormone measurements with multispectral imaging-based precision phenotyping to gain insights into the molecular basis of Z -3-hexenyl acetate-induced resistance (Z-3-HAC-IR) in rice. Furthermore, we evaluated the efficacy of Z -3-HAC-IR against a panel of economically significant rice pathogens: Pyricularia oryzae , Rhizoctonia solani , Xanthomonas oryzae pv. oryzae , Cochliobolus miyabeanus , and Meloidogyne graminicola. Our data revealed rapid induction of jasmonate metabolism and systemic induction of plant immune responses upon Z -3-HAC exposure, as well as a transient allocation cost due to accelerated chlorophyll degradation and nutrient remobilization. Z -3-HAC-IR proved effective against all tested pathogens except for C. miyabeanus , including against the (hemi)biotrophs M. graminicola, X. oryzae pv. oryzae , and P. oryzae. The Z -3-HAC-IR phenotype was lost in the jasmonate (JA)-deficient hebiba mutant, which confirms the causal role of JA in Z -3-HAC-IR. Together, our results show that GLV exposure in rice induces broad-spectrum, JA-mediated disease resistance with limited allocation costs, and may thus be a promising alternative crop protection approach. [ABSTRACT FROM AUTHOR]

Abstract Background The biochemical makeup of grape berries at harvest is essential for wine quality and depends on a fine transcriptional regulation occurring during berry development. In this study, we conducted a comprehensive survey of transcriptomic and metabolomic changes occurring in different berry tissues and developmental stages of the ancient grapes Aglianico and Falanghina to establish the patterns of the secondary metabolites contributing to their wine aroma and investigate the underlying transcriptional regulation. Results Over two hundred genes related to aroma were found, of which 107 were differentially expressed in Aglianico and 99 in Falanghina. Similarly, 68 volatiles and 34 precursors were profiled in the same samples. Our results showed a large extent of transcriptomic and metabolomic changes at the level of isoprenoids (terpenes, norisoprenoids), green leaf volatiles (GLVs), and amino acid pathways, although the terpenoid metabolism was the most distinctive for Aglianico, and GLVs for Falanghina. Co-expression analysis that integrated metabolome and transcriptome data pinpointed 25 hub genes as points of biological interest in defining the metabolic patterns observed. Among them, three hub genes encoding for terpenes synthases (VvTPS26, VvTPS54, VvTPS68) in Aglianico and one for a GDP-L-galactose phosphorylase (VvGFP) in Falanghina were selected as potential active player underlying the aroma typicity of the two grapes. Conclusion Our data improve the understanding of the regulation of aroma-related biosynthetic pathways of Aglianico and Falanghina and provide valuable metabolomic and transcriptomic resources for future studies in these varieties.

Green leaf volatiles (GLVs) are important in giving grape a fresh and green aroma. But the changes in GLVs during the phenological development of grapevines are not well known. This study analyzed the GLVs and transcription levels of associated biosynthetic genes in six grape species from the Loess Plateau region at five stages of maturation. Thirteen GLVs were detected, showing unique patterns for each grape type at various growth phases. The primary components in six grapes were (E)-2-hexenal, (E)-2-hexen-1-ol, and hexanal. With the exception of Cabernet Franc in 2019, the overall GLV contents of the six types generally increased during growth and development, peaking or stabilizing at harvest. And Sauvignon Blanc, Cabernet Gernischt, and Cabernet Sauvignon exhibited higher total contents among the varieties. PLS-DA analysis revealed 3-hexenal’s high VIP scores across two years, underscoring its critical role in grape variety classification. Correlation analysis revealed a strong positive correlation between the levels of hexanal, 1-hexanol, (E)-2-hexen-1-ol, (Z)-3-hexenyl acetate, nonanal, and (E, E)-2,6-nonadienal and the expression of VvHPL and VvAAT genes in the LOX-HPL pathway. Specifically, VvHPL emerges as a potential candidate gene responsible for species–specific differences in GLV compounds. Comprehending the changing patterns in the biosynthesis and accumulation of GLVs offers viticulturists and enologists the opportunity to devise targeted strategies for improving the aromatic profile of grapes and wines.

Many aldehydes are volatile compounds with distinct and characteristic olfactory properties. The aldehydic functional group is reactive and, as such, an invaluable chemical multi‐tool to make all sorts of products. Owing to the reactivity, the selective synthesis of aldehydic is a challenging task. Nature has evolved a number of enzymatic reactions to produce aldehydes, and this review provides an overview of aldehyde‐forming reactions in biological systems and beyond. Whereas some of these biotransformations are still in their infancy in terms of synthetic applicability, others are developed to an extent that allows their implementation as industrial biocatalysts. [ABSTRACT FROM AUTHOR]

Background: The biochemical makeup of grape berries at harvest is essential for wine quality and depends on a fine transcriptional regulation occurring during berry development. In this study, we conducted a comprehensive survey of transcriptomic and metabolomic changes occurring in different berry tissues and developmental stages of the ancient grapes Aglianico and Falanghina to establish the patterns of the secondary metabolites contributing to their wine aroma and investigate the underlying transcriptional regulation. Results: Over two hundred genes related to aroma were found, of which 107 were differentially expressed in Aglianico and 99 in Falanghina. Similarly, 68 volatiles and 34 precursors were profiled in the same samples. Our results showed a large extent of transcriptomic and metabolomic changes at the level of isoprenoids (terpenes, norisoprenoids), green leaf volatiles (GLVs), and amino acid pathways, although the terpenoid metabolism was the most distinctive for Aglianico, and GLVs for Falanghina. Co-expression analysis that integrated metabolome and transcriptome data pinpointed 25 hub genes as points of biological interest in defining the metabolic patterns observed. Among them, three hub genes encoding for terpenes synthases (VvTPS26, VvTPS54, VvTPS68) in Aglianico and one for a GDP-L-galactose phosphorylase (VvGFP) in Falanghina were selected as potential active player underlying the aroma typicity of the two grapes. Conclusion: Our data improve the understanding of the regulation of aroma-related biosynthetic pathways of Aglianico and Falanghina and provide valuable metabolomic and transcriptomic resources for future studies in these varieties. [ABSTRACT FROM AUTHOR]

We assessed attraction of pine engraver, Ips pini (Say) (Coleoptera: Curculionidae; Scolytinae), to pheromone-baited funnel traps treated with repellent semiochemicals in ponderosa pine, Pinus ponderosa var. scopulorum Engelm. forests in northern Arizona. Treatments included: 1) baited control (B, ipsdienol + lanierone), 2) 70 g of SPLAT Verb (a flowable, biodegradable formulation containing 10% verbenone, ISCA Technologies Inc. Riverside, CA, USA) + B, 3) 70 g of SPLAT Verb + (E)-2-hexen-1-ol+(Z)-2-hexen-1-ol + acetophenone + B, 4) 7.84-g verbenone pouch (Product #3413, Synergy Semiochemicals Corp. Delta, British Columbia, Canada) + B, and 5) 7.84-g verbenone pouch + (E)-2-hexen-1-ol+(Z)-2-hexen-1-ol + acetophenone + B. In total, 472 I. pini were collected. Trap catches were highest in baited traps and declined significantly with the addition of both formulations of verbenone. Traps treated with SPLAT Verb caught significantly fewer I. pini and male I. pini than those treated with verbenone pouches. The addition of (E)-2-hexen-1-ol+(Z)-2-hexen-1-ol + acetophenone to SPLAT Verb and the verbenone pouch had no effect on trap catch. Verbenone has potential as an effective tool for protecting P. ponderosa trees and slash from I. pini in northern Arizona, but the addition of (E)-2-hexen-1-ol+(Z)-2-hexen-1-ol + acetophenone to verbenone is unwarranted. [ABSTRACT FROM AUTHOR]

Intraguild interactions are known to trigger competition among phytophagous insects that depend on the same food source, which may have implications on natural enemy performance. Here, we tested the hypothesis that intraguild interactions between the greenhouse whitefly, Trialeurodes vaporariorum, and the South American tomato pinworm, Phthorimaea absoluta on the host plant tomato would affect performance of the pinworm ectoparasitoid Bracon nigricans. In oviposition bioassays, P. absoluta females significantly laid more eggs and were attracted to tomato plants infested with T. vaporariorum than uninfested plants. Additionally, T. vaporariorum infestation decreased B. nigricans parasitism on P. absoluta larvae and attraction to tomato plants. In coupled gas chromatography-electroantennographic detection (GC-EAD) recordings, antennae of P. absoluta and B. nigricans females detected 18 and 15 components, respectively from the herbivore-induced volatiles, which were identified by GC-mass spectrometry (GC-MS) as green leaf volatiles (GLVs) and terpenes. In dose-response behavioral assays, P. absoluta and B. nigricans responses varied with the composition and concentration of blends and individual compounds tested. Whereas P. absoluta was attracted to GLVs and terpenes, B. nigricans avoided most of these chemicals, especially the GLV (E)-2-hexenal and terpenes δ-3-carene, and (E)-caryophyllene. The results suggest that herbivore intraguild interactions can influence the behavioral ecology and performance of natural enemies which may have evolutionary significance. Also, these specific GLVs and terpenes can be exploited in the management of P. absoluta.

Green leaf volatiles (GLVs), play important roles in the green and fresh aroma characteristics of grape berries. The evolution of GLV profiles regarding the varietal difference during grapevine phenological ripening is not well understood. This study generated the GLV profiles of five Vitis vinifera L. cultivars (‘Cabernet Sauvignon,’ ‘Cabernet Franc,’ ‘Cabernet Gernischt,’ ‘Chardonnay,’ and ‘Sauvignon Blanc’) at five ripening stages. GLVs were distinctive at different E-L stages for each grape variety. (E)-2-hexen-1-ol, 1-hexanol, and hexanal were the dominant components in all mature berries. In terms of total GLV content, all varieties reached the maximum at maturity in the 2019 vintage, and the total GLV content was higher in mature Sauvignon Blanc and Cabernet Sauvignon grapes. In the 2020 vintage, the total GLV content in Chardonnay and Sauvignon Blanc berries rapidly accumulated at veraison and peaked before harvest. The present results could help winemakers create a good balance of wine aroma.

Plants have evolved diverse secondary metabolites to counteract biotic stress. Volatile organic compounds (VOCs) are released upon herbivore attack or pathogen infection. Recent studies suggest that VOCs can act as signalling molecules in plant defence and induce resistance in distant organs and neighbouring plants. However, knowledge is lacking on the function of VOCs in biotrophic fungal infection on cereal plants.We analysed VOCs emitted by 13 ± 1‐day‐old barley plants (Hordeum vulgare L.) after mechanical wounding using passive absorbers and TD‐GC/MS. We investigated the effect of pure VOC and complex VOC mixtures released from wounded plants on the barley–powdery mildew interaction by pre‐exposure in a dynamic headspace connected to a powdery mildew susceptibility assay. Untargeted metabolomics and lipidomics were applied to investigate metabolic changes in sender and receiver barley plants.Green leaf volatiles (GLVs) dominated the volatile profile of wounded barley plants, with (Z)‐3‐hexenyl acetate (Z3HAC) as the most abundant compound. Barley volatiles emitted after mechanical wounding enhanced resistance in receiver plants towards fungal infection. We found volatile‐mediated modifications of the plant–pathogen interaction in a concentration‐dependent manner. Pre‐exposure with physiologically relevant concentrations of Z3HAC resulted in induced resistance, suggesting that this GLV is a key player in barley anti‐pathogen defence.The complex VOC mixture released from wounded barley and Z3HAC induced e.g. accumulation of chlorophyll, linolenic acid and linolenate‐conjugated lipids, as well as defence‐related secondary metabolites, such as hordatines in receiving plants. Barley VOCs hence induce a complex physiological response and disease resistance in receiver plants. [ABSTRACT FROM AUTHOR]

To investigate in detail the volatilomes of various Brassicaceae species, landraces, and accessions, and to extract specific volatile markers, volatile aroma compounds were isolated from plant samples by headspace solid-phase microextraction and analyzed by gas chromatography/mass spectrometry (HS-SPME-GC/MS). The data obtained were subjected to uni- and multivariate statistical analysis. In general, two cabbage (Brassica oleracea L. var. capitata) landraces emitted the lowest amounts of volatiles generated in the lipoxygenase (LOX) pathway. Wild species Brassica incana Ten. and Brassica mollis Vis. were characterized by relatively high trans-2-hexenal/cis-3-hexen-1-ol ratio in relation to other investigated samples. A Savoy cabbage (Brassica oleracea L. var. sabauda) cultivar and three kale (Brassica oleracea L. var. acephala) accessions exhibited particular similarities in the composition of LOX volatiles, while the LOX volatilome fraction of B. incana and B. mollis partially coincided with that of another wild species, Diplotaxis tenuifolia L. Regarding volatiles formed in the glucosinolate (GSL) pathway, Savoy cabbage and wild species B. incana, B. mollis, and D. tenuifolia showed more intense emission of isothiocyanates than cabbage and kale. Diplotaxis tenuifolia showed a rather limited production of nitriles. The results of this study contribute to the general knowledge about volatile composition from various Brassicaceae species, which could be exploited for their better valorization. Future studies should focus on the influence of various environmental, cultivation, and post-harvest factors to obtain data with a higher level of applicability in practice. [ABSTRACT FROM AUTHOR]

Soil microbiota can either slow down or facilitate plant invasions through their effects on plant performance. Associations with soil microbiota can also modify other plant traits such as herbivore resistance, which can indirectly affect the outcome of plant introductions.We studied the effects of soil microbiota on the perennial herbaceous legume Lupinus polyphyllus that hosts nitrogen‐fixing mutualistic bacteria. We compared the plant performance, herbivore resistance and volatile organic compounds (VOCs) of plants from native (North American) and invasive (Finnish) populations of the species that were inoculated with intact or autoclaved soil from an invasive population.We found that plants of both origins greatly benefited from the intact soil inoculum with respect to all performance measures considered, suggesting that beneficial nitrogen‐fixing rhizobia in the soil play a major role in shaping plant phenotypes. For three traits, effects of the intact soil inoculum were stronger in plants of native origin than in plants of invasive origin (number of leaves, herbivore resistance and total biomass). With the intact soil inoculum, plants of invasive origin were more resistant to snails than plants of native origin. Strikingly, differences in resistance to snails between plants of different origins disappeared entirely when soil microbes were reduced. Soil inoculum treatment altered the composition of the leaf VOC bouquet similarly regardless of plant origin.Synthesis. These results demonstrate the ability of Lupinus polyphyllus to associate with and benefit from putatively novel soil microbiota including rhizobia, which has likely contributed to its invasion success. Furthermore, it appears that the invasive populations have adapted to be less reliant on their symbionts, which further facilitates species spread. To our knowledge, this is the first study to demonstrate that differences in herbivore resistance between native and invasive plant populations of the same species can depend entirely on soil microbiota. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) play an important role in plant ecology and can be useful in pest management. This work characterises, for the first time, the VOC emissions of six industrial hemp (Cannabis sativa L.) cultivars grown in New Zealand: CFX-2, CRS-1, Ferimon 12, Katani, Futura 75, and Finola. Volatiles emitted from flowers and foliage of eight-week-old plants were collected using a dynamic headspace sampling method and analysed using gas chromatography coupled to mass spectrometry. We assessed the effect of cultivar, sex (monoecious, male, and female), and site (i.e., two sites differing in soil types, maintained under irrigation and rain-fed conditions) on VOC emissions. Thirty-five volatile compounds were tentatively identified from the headspace samples of hemp plants, but none of the cultivars emitted all 35 compounds. β-Myrcene was the most abundant compound in most cultivars. Overall, there was a significant effect of sex, and the interaction of sex and cultivar on the volatile profiles, but no effect of site. Female plants typically emitted more volatiles than their male counterparts and monoecious cultivars. The main compounds driving the difference between cultivars and sexes were (Z)- and (E)-β-ocimene. We hypothesize that differences in emission emerged as a defence strategy to protect costly female flowers from herbivores (since C. sativa is wind pollinated), but this hypothesis needs further testing. We recommend additional studies exploring how biotic and abiotic factors influence hemp VOC emissions, changes in VOCs throughout the crop cycle, the role of VOCs in plant-insect interactions and their use in pest management. [ABSTRACT FROM AUTHOR]

Climate change is one of the main challenges for actual and future generations. Global warming affects plants and animals and is responsible for considerable crop loss. This study studied the influence of antagonist successive stresses, cold–heat and heat–cold, on two medicinal plants Ocimum basilicum L. and Salvia officinalis L. The photosynthetic parameters decreased for plants under the variation of subsequent stress. Net assimilation rates and stomatal conductance to water vapor are more affected in the case of plants under cold–heat consecutive stress than heat–cold successive stress. Emissions of volatile organic compounds have been enhanced for plants under successive stress when compared with control plants. Chlorophyll concentrations for plants under successive stress decreased for basil and sage plants. The total phenolic and flavonoid contents were not affected by the successive stresses when compared with the plants under only one type of treatment. [ABSTRACT FROM AUTHOR]

Climate change will determine a sharp increase in carbon dioxide in the following years. To study the influence of elevated carbon dioxide on plants, we grew 13 different species and varieties from the Brassicaceae family at three carbon dioxide concentrations: 400, 800, and 1200 ppmv. The photosynthetic parameters (assimilation rate and stomatal conductance to water vapor) increase for all species. The emission of monoterpenes increases for plants grown at elevated carbon dioxide while the total polyphenols and flavonoids content decrease. The chlorophyll content is affected only for some species (such as Lipidium sativum), while the β-carotene concentrations in the leaves were not affected by carbon dioxide. [ABSTRACT FROM AUTHOR]

Green leaf volatiles (GLVs) are initially formed in the form of aldehydes, and then converted to alcohol and ester forms by the enzymes from plants. However, it remains unclear whether and how plant microbes work with aldehyde GLVs, especially under stressed conditions. Here, transcriptional response of cold-pretreated Pantoea agglomerans KSC03, an endophyte from Astragalus membranaceus var. mongholicus roots to E-2-hexenal was investigated and verified by real-time PCR and GC–MS after the time length of cold pretreatment was optimized. The results revealed that a 12-h cold stress was the most effective for KSC03 to trigger positive response to E-2-hexenal as far as the cell density was concerned. Transcriptome analysis showed that differentially expressed genes induced by E-2-hexenal were enriched in the following pathways: ABC transporter, phosphotransferase system, nitrotoluene degradation, and metabolisms of hexose and butanoate. Amongst, the upregulated transcription of gene3176 and gene4782 encoding N-ethylmaleimide reductase and diacetyl reductase in E-2-hexenal treatment was confirmed by real-time PCR. So did the enhanced production of 2,3-butanediol triggered by E-2-hexenal. Additionally, the transcription of gene3176 and gene4782 and the production of 2,3-butanediol chronologically reached their peaks in the E-2-hexenal-treated cells at the stationary phase. The results also indicated that exogenous E-2-hexanal passed through the cell membrane at the lag/early logarithmic phase and could not be utilized directly. In summary, E-2-hexenal triggers the positive cell response of cold-pretreated KSC03 at the transcriptional and metabolic levels in a time-length dependent manner. [ABSTRACT FROM AUTHOR]

Several herbivorous caterpillars contain effectors in their oral secretions that alter the emission of green leaf volatiles (GLVs) produced by the plants upon which the caterpillars are feeding. These effectors include an isomerase, a fatty acid dehydratase (FHD), and a heat-stable hexenal trapping (HALT) molecule. GLVs serve as signaling compounds in plant-insect interactions and inter-and intra-plant communication. However, it is not known whether these GLV-altering effectors are common among herbivorous caterpillars, or the evolutionary context of these effectors in relation to GLV emission by host plants in response to feeding damage. Here, we examined the distribution and activity of the isomerase, FHD, and HALT effectors across 10 species spanning 7 lepidopteran families. Six of the 10 species possessed all three effectors in their oral secretions. Activity from the HALT and FHD effectors was observed in all examined caterpillar species, while activity from the isomerase effector varied in some species and was absent in others. There was no discernable pattern in effector activity based on evolutionary divergence, since individual species within a family did not possess similar mechanisms to alter GLV emission. These data, demonstrating the GLV-altering effectors acting at different steps in the GLV biosynthetic pathway and present in the examined caterpillar species at different combinations with different activities, highlight the importance of these effectors in changing the emission of these compounds during caterpillar herbivory. Understanding the prevalence and roles of GLV-altering effectors and GLV emission itself will open new research areas in the dynamics of plant-insect interactions. [ABSTRACT FROM AUTHOR]

Green leaf volatiles (GLV) are essentially produced by the green parts of plants upon damage. GLV are mainly 6-carbon molecules derived from fatty acids through the hydroperoxide lyase pathway and can serve as airborne signals to other parts of the same plant and to neighboring plants and help to protect them against biotic and abiotic stresses. However, while the biosynthesis is generally well understood, little is known about how plants regulate the production of these important signaling molecules. To better understand how the developmental stage of the plant affects aldehyde GLV production, we selected Zea mays and Vigna radiata to represent mono- and dicot plants for this analysis. We show that the capacity to produce aldehyde GLV strongly depends on the developmental stage of the plant. Major differences in the quantity, and in the quality of these compounds were found, not only in leaves from different developmental stages, but also in different areas within a leaf. The results demonstrate that the capacity to produce GLV varies significantly within a plant and the potential implications of these findings are discussed. [ABSTRACT FROM AUTHOR]

Spruce beetle, Dendroctonus rufipennis Kirby (Coleoptera: Curculionidae), is a lethal pest of spruce trees in North America. Despite decades of research, a semiochemical repellent that consistently and effectively protects spruce trees remains elusive. We evaluated the efficacy of 3-methyl-2-cyclohexen-1-one (MCH) in a proprietary, volatile compound release technology (SPLAT) alone and with two adjuvants, Acer kairomone blend (AKB) and acetophenone + green leaf volatiles (PLUS) to protect individually treated Picea engelmannii Parry ex. Engelm. (Pinales: Pinaceae), and Pi. engelmannii within 11.3-m radius of the individually treated trees from colonization and mortality attributed to D. rufipennis in western Wyoming. Ninety-one Pi. engelmannii were baited with frontalin and randomly assigned to one of seven treatments (n = 13): 3.5 g of MCH applied as SPLAT MCH (SPLAT3.5), 3.5AKB, 3.5PLUS, 7 g of MCH applied as SPLAT MCH (SPLAT7), 7AKB, 7PLUS, and baited control (bait only). All repellents except SPLAT3.5 and SPLAT7 significantly reduced colonization of individually treated Pi. engelmannii compared to the baited control. 3.5PLUS, 7AKB, and 7PLUS reduced colonization most effectively, and all repellents significantly reduced mortality of individually treated Pi. engelmannii compared to the baited control. All repellents also significantly reduced colonization and mortality of neighboring Pi. engelmannii. [ABSTRACT FROM AUTHOR]

This review highlights the importance of volatile organic compounds (VOCs) in plant–plant interactions, covering the defence, growth, and reproduction responses in recipient plants upon VOC exposure. It is firmly established that plants respond to biotic and abiotic stimuli by emitting volatile organic compounds (VOCs). These VOCs provide information on the physiological status of the emitter plant and are available for detection by the whole community. In the context of plant–plant interactions, research has focused mostly on the defence-related responses of receiver plants. However, responses may span hormone signalling and both primary and secondary metabolism, and ultimately affect plant fitness. Here we present a synthesis of plant–plant interactions, focusing on the effects of VOC exposure on receiver plants. An overview of the important chemical cues, the uptake and conversion of VOCs, and the adsorption of VOCs to plant surfaces is presented. This is followed by a review of the substantial VOC-induced changes to receiver plants affecting both primary and secondary metabolism and influencing plant growth and reproduction. Further research should consider whole-plant responses for the effective evaluation of the mechanisms and fitness consequences of exposure of the receiver plant to VOCs. [ABSTRACT FROM AUTHOR]

Hexanal belongs to green leaf volatiles that function as signal molecules in plants. However, it remains elusive whether and how hexanal functions in herbal medicines besides imparting unique flavor. In this study, the effects of hexanal and Pantoea agglomerans KSC03 on plant growth and secondary metabolism were investigated in medicinal plant Astragalus membranaceus var. mongholicus by treating the seedlings with hexanal, KSC03, and their combination. Biomass yield and the contents of chlorophyll a and b in mature leaves were used as indexes as well as the contents of bioactive isoflavones in the roots. Meanwhile, lipoxygenase (LOX) inhibitor phenidone was applied 48 h before hexanal treatment to obtain the LOXlow seedlings to understand signal roles of LOX pathway in the accumulations of bioactive isoflavones in the roots under hexanal and KSC03 treatments. The results revealed that hexanal alone and its combination with KSC03 significantly increased the shoot and root yields, and hexanal + KSC03 showed stronger promotion on the shoot yield, which coincided with significantly enhanced accumulations of ononin and calycosin-7-O-β-d-glycoside in hexanal + KSC03 treatment. Hexanal + KSC03 also alleviated the detrimental chlorophylls cycle compared with hexanal alone. Except for the combined treatment, phenidone pretreatment greatly enhanced the concentrations of ononin and calycosin-7-O-β-d-glycoside in the roots of the control and the application of hexanal and KSC03 alone. In conclusion, hexanal + KSC03 treatment was more beneficial on plant growth and accumulations of bioactive isoflavones in the roots of A. membranaceus var. mongholicus, partially due to the attenuated inhibition of LOX signaling. [ABSTRACT FROM AUTHOR]

To investigate in detail the volatilomes of various Brassicaceae species, landraces, and accessions, and to extract specific volatile markers, volatile aroma compounds were isolated from plant samples by headspace solid-phase microextraction and analyzed by gas chromatography/mass spectrometry (HS-SPME-GC/MS). The data obtained were subjected to uni- and multivariate statistical analysis. In general, two cabbage (Brassica oleracea L. var. capitata) landraces emitted the lowest amounts of volatiles generated in the lipoxygenase (LOX) pathway. Wild species Brassica incana Ten. and Brassica mollis Vis. were characterized by relatively high trans-2-hexenal/cis-3-hexen-1-ol ratio in relation to other investigated samples. A Savoy cabbage (Brassica oleracea L. var. sabauda) cultivar and three kale (Brassica oleracea L. var. acephala) accessions exhibited particular similarities in the composition of LOX volatiles, while the LOX volatilome fraction of B. incana and B. mollis partially coincided with that of another wild species, Diplotaxis tenuifolia L. Regarding volatiles formed in the glucosinolate (GSL) pathway, Savoy cabbage and wild species B. incana, B. mollis, and D. tenuifolia showed more intense emission of isothiocyanates than cabbage and kale. Diplotaxis tenuifolia showed a rather limited production of nitriles. The results of this study contribute to the general knowledge about volatile composition from various Brassicaceae species, which could be exploited for their better valorization. Future studies should focus on the influence of various environmental, cultivation, and post-harvest factors to obtain data with a higher level of applicability in practice.

Plants have evolved a vast array of secondary metabolites that help defend them against natural enemy attack. The production of these secondary metabolites is influenced by environmental factors, such as temperature, rainfall (soil water availability) and atmospheric [CO2], which may be altered under climate change. This study aimed to test how two of these environmental factors, namely soil water availability and [CO2], will affect secondary metabolite and biomass production in Eucalypts. To investigate this, we measured secondary metabolite and biomass production of three Eucalypt species (Eucalyptus grandis, E. moluccana, E. saligna) grown under ambient and elevated [CO2] (400 and 600 ppm, respectively) and water‐stressed and well‐watered conditions, in a fully factorial glasshouse experiment. The secondary metabolites measured were foliar phenolic concentration as well as terpene and green leaf volatile emissions. We found that water stress did not alter secondary metabolite production. Unsurprisingly, the water‐stressed plants maximised their water uptake potential by reducing shoot biomass but maintaining root biomass. The detrimental effects of water stress on shoot biomass production were not reduced under elevated [CO2] compared to ambient [CO2], despite all species experiencing significant reductions in stomatal conductance. Further, [CO2] as a single factor did not have a significant effect on species' net carbon gain, with an increase in green leaf volatile emissions under elevated [CO2] being mitigated by a reduction in shoot biomass production. These results suggest that reductions in carbon gains due to water stress will affect the growth of Eucalypts rather than their chemical defence capabilities. [ABSTRACT FROM AUTHOR]

Featured Application: The volatile organic compounds emission from plants could be used as an indicator of stress. Drought and flooding are some of the most common stressful conditions for plants. Due to the recent climate changes, they can occur one after another. This study is focused on the effect of antagonistic abiotic stress such as drought and flooding on the different metabolites from Ocimum basilicum leaves. Six-week-old plants of Ocimum basilicum were exposed to drought or flooding stress for 15 days, followed by antagonist stress for 14 days. The assimilation rates decrease drastically for plants under consecutive stresses from 18.9 to 0.25 µmol m−2 s−1 starting at day 3 of treatment. The stomatal conductance to water vapor gs was also reduced from 86 to 29 mmol m−2 s−1. The emission of green leaf volatiles compounds increases from 0.14 to 2.48 nmol m−2 s−1, and the emission of monoterpenes increased from 2.00 to 7.37 nmol m−2 s−1. The photosynthetic pigment concentration (chlorophyll a and b, and β-carotene), the flavonoid content, and total phenolic content decrease for all stressed plants. The results obtained in this study could indicate that the water status (drought and/or flooding) directly impacts basil plants' physiological parameters and secondary metabolites. [ABSTRACT FROM AUTHOR]

Prolonged drought stress combined with high leaf temperatures can induce programmed leaf senescence involving lipid peroxidation, and the loss of net carbon assimilation during early stages of tree mortality. Periodic droughts are known to induce widespread tree mortality in the Amazon rainforest, but little is known about the role of lipid peroxidation during drought-induced leaf senescence. In this study, we present observations of green leaf volatile (GLV) emissions during membrane peroxidation processes associated with the combined effects of high leaf temperatures and drought-induced leaf senescence from individual detached leaves and a rainforest ecosystem in the central Amazon. Temperature-dependent leaf emissions of volatile terpenoids were observed during the morning, and together with transpiration and net photosynthesis, showed a post-midday depression. This post-midday depression was associated with a stimulation of C₅ and C₆ GLV emissions, which continued to increase throughout the late afternoon in a temperature-independent fashion. During the 2010 drought in the Amazon Basin, which resulted in widespread tree mortality, green leaf volatile emissions (C₆ GLVs) were observed to build up within the forest canopy atmosphere, likely associated with high leaf temperatures and enhanced drought-induced leaf senescence processes. The results suggest that observations of GLVs in the tropical boundary layer could be used as a chemical sensor of reduced ecosystem productivity associated with drought stress.

Volatile organic compounds (VOCs) play an important role in plant ecology and can be useful in pest management. This work characterises, for the first time, the VOC emissions of six industrial hemp (Cannabis sativa L.) cultivars grown in New Zealand: CFX-2, CRS-1, Ferimon 12, Katani, Futura 75, and Finola. Volatiles emitted from flowers and foliage of eight-week-old plants were collected using a dynamic headspace sampling method and analysed using gas chromatography coupled to mass spectrometry. We assessed the effect of cultivar, sex (monoecious, male, and female), and site (i.e., two sites differing in soil types, maintained under irrigation and rain-fed conditions) on VOC emissions. Thirty-five volatile compounds were tentatively identified from the headspace samples of hemp plants, but none of the cultivars emitted all 35 compounds. β-Myrcene was the most abundant compound in most cultivars. Overall, there was a significant effect of sex, and the interaction of sex and cultivar on the volatile profiles, but no effect of site. Female plants typically emitted more volatiles than their male counterparts and monoecious cultivars. The main compounds driving the difference between cultivars and sexes were (Z)- and (E)-β-ocimene. We hypothesize that differences in emission emerged as a defence strategy to protect costly female flowers from herbivores (since C. sativa is wind pollinated), but this hypothesis needs further testing. We recommend additional studies exploring how biotic and abiotic factors influence hemp VOC emissions, changes in VOCs throughout the crop cycle, the role of VOCs in plant-insect interactions and their use in pest management.

It is known that undamaged plants that have been exposed to volatiles from damaged con- or heterospecific plants become more resistant against herbivores. This is one of the plants’ induced resistant responses against herbivores. To test whether this response can be used for rice production, we conducted the following experiments over 2 years (2012 and 2013). Rice seedlings were first planted in the rice seedling bed for 2 weeks in early May. There, half of the rice seedlings were exposed to artificially damaged weed volatiles three times for 12 days (treated plants). Weeds were randomly collected from the areas that were >100 m away from the seedling bed and the rice paddy fields. The remaining seedlings were not exposed (control plants). In the middle of May, bunches (ca. three seedlings per bunch) were transplanted to the rice paddy field. In July, leaf damage was observed. The total number of leaves in the treated and control plants was not significantly different. In contrast, the total number of damaged leaves in the treated plants was significantly lower than that in the control plants. In September, rice grains were harvested. The average weight of a rice grain from the treated and control plants was not significantly different. However, the weight of grains per bunch of treated plants was significantly higher than that of control plants; this indicated a significant increase of the number of grains by 23% in 2012 and by 18% in 2013 in the treated plants compared to that in the control plants. The volatiles emitted from the weeds included monoterpenoids (40.4% in total), green leaf volatiles (46.5%), short-chain alcohols (5.3%), short-chain ketone (5.4%), short-chain acetate (0.5%), short-chain aldehyde (1.1%), and hydrocarbon (0.7%). These results suggest that exposure of volatiles from artificially damaged weeds to rice seedlings has the potential to increase rice production.

Tea (Camellia sinensis L.), a woody perennial plant native to China and Southeast Asia, has a 30–50 years lifespan. The occurrence of insect pests and the interactions with their host plants directly stimulate very many significant responses upon the physiological and quality parameters of tea plants. In this review, we attempted to analyze the effects of elevated atmospheric carbon dioxide (eCO2) on tea plant physiological and functional parameters, including key genes involved in bio-synthetic pathways, and also the tea quality parameters altered by the insect pest damage especially under eCO2. It has been demonstrated that the tea quality is associated with various biochemical constituents present in tea infusion, flavor and aroma characteristics of tea. The biochemical composition of tea leaf is dependent on environmental growth conditions and the genetic makeup of tea plants. In addition, insect pests’ immediate response to eCO2 propels insect herbivores’ occurrence and damage on tea plants in an extensive scale, especially under climate change. It is presumed that intricate interaction of eCO2 and insect pests’ occurrence and damage directly affects tea quality, rendering the tea with augmented aroma, enhanced esthetic pleasantness, and desirable flavor, thus making the green tea more desirable and favorable.

It is known that undamaged plants that have been exposed to volatiles from damaged con- or heterospecific plants become more resistant against herbivores. This is one of the plants' induced resistant responses against herbivores. To test whether this response can be used for rice production, we conducted the following experiments over 2 years (2012 and 2013). Rice seedlings were first planted in the rice seedling bed for 2 weeks in early May. There, half of the rice seedlings were exposed to artificially damaged weed volatiles three times for 12 days (treated plants). Weeds were randomly collected from the areas that were >100 m away from the seedling bed and the rice paddy fields. The remaining seedlings were not exposed (control plants). In the middle of May, bunches (ca. three seedlings per bunch) were transplanted to the rice paddy field. In July, leaf damage was observed. The total number of leaves in the treated and control plants was not significantly different. In contrast, the total number of damaged leaves in the treated plants was significantly lower than that in the control plants. In September, rice grains were harvested. The average weight of a rice grain from the treated and control plants was not significantly different. However, the weight of grains per bunch of treated plants was significantly higher than that of control plants; this indicated a significant increase of the number of grains by 23% in 2012 and by 18% in 2013 in the treated plants compared to that in the control plants. The volatiles emitted from the weeds included monoterpenoids (40.4% in total), green leaf volatiles (46.5%), short-chain alcohols (5.3%), short-chain ketone (5.4%), short-chain acetate (0.5%), short-chain aldehyde (1.1%), and hydrocarbon (0.7%). These results suggest that exposure of volatiles from artificially damaged weeds to rice seedlings has the potential to increase rice production. [ABSTRACT FROM AUTHOR]

Abstract Background Forage and turf grasses are routinely cut and grazed upon throughout their lifecycle. When grasses are cut or damaged, they rapidly release a volatile chemical cocktail called green leaf volatiles (GLV). Previously we have shown that mechanical wounding or exposure to GLV released from cut grass, activated a Lt 46 kDa mitogen-activated protein kinase (MAPK) within 3 min and a 44 kDa MAPK within 15–20 min in the model grass species Lolium temulentum (Lt). Currently very little is known concerning the perception, signaling or molecular responses associated with wound stress in grasses. Since GLV are released during wounding, we wanted to investigate what genes and signaling pathways would be induced in undamaged plants exposed to GLV. Results RNA-Seq generated transcriptome of Lolium plants exposed to GLV identified 4308 up- and 2794 down-regulated distinct differentially-expressed sequences (DES). Gene Ontology analysis revealed a strong emphasis on signaling, response to stimulus and stress related categories. Transcription factors and kinases comprise over 13% of the total DES found in the up-regulated dataset. The analysis showed a strong initial burst within the first hour of GLV exposure with over 60% of the up-regulated DES being induced. Specifically sequences annotated for enzymes involved in the biosynthesis of jasmonic acid and other plant hormones, mitogen-activated protein kinases and WRKY transcription factors were identified. Interestingly, eleven DES for ferric reductase oxidase, an enzyme involved in iron uptake and transport, were exclusively found in the down-regulated dataset. Twelve DES of interest were selected for qRT-PCR analysis; all displayed a rapid induction one hour after GLV exposure and were also strongly induced by mechanical wounding. Conclusion The information gained from the analysis of this transcriptome and previous studies suggests that GLV released from cut grasses transiently primes an undamaged plant’s wound stress pathways for potential oncoming damage, and may have a dual role for inter- as well as intra-plant signaling.

Climate change is one of the main challenges for actual and future generations. Global warming affects plants and animals and is responsible for considerable crop loss. This study studied the influence of antagonist successive stresses, cold–heat and heat–cold, on two medicinal plants Ocimum basilicum L. and Salvia officinalis L. The photosynthetic parameters decreased for plants under the variation of subsequent stress. Net assimilation rates and stomatal conductance to water vapor are more affected in the case of plants under cold–heat consecutive stress than heat–cold successive stress. Emissions of volatile organic compounds have been enhanced for plants under successive stress when compared with control plants. Chlorophyll concentrations for plants under successive stress decreased for basil and sage plants. The total phenolic and flavonoid contents were not affected by the successive stresses when compared with the plants under only one type of treatment.

Climate change will determine a sharp increase in carbon dioxide in the following years. To study the influence of elevated carbon dioxide on plants, we grew 13 different species and varieties from the Brassicaceae family at three carbon dioxide concentrations: 400, 800, and 1200 ppmv. The photosynthetic parameters (assimilation rate and stomatal conductance to water vapor) increase for all species. The emission of monoterpenes increases for plants grown at elevated carbon dioxide while the total polyphenols and flavonoids content decrease. The chlorophyll content is affected only for some species (such as Lipidium sativum), while the β-carotene concentrations in the leaves were not affected by carbon dioxide.

The transition from a perennial to an annual life cycle, as well as domestication, are expected to increase plant growth and reproduction at the same time that anti-herbivore defences are reduced. Here, we investigated the effects of the life-history transition (the perennial teosinte Zea diploperennis to the annual teosinte Z. mays ssp. mexicana) and domestication of Zea (annual teosinte to the modern maize Z. mays ssp. mays) on direct and indirect defences against the fall armyworm Spodoptera frugiperda. The direct defence of Zea was assessed by larval survival and nutritional indices based on food intake and utilisation. Indirect defence was measured in terms of the olfactory preference of the night-active predatory earwig Doru luteipes for nocturnal herbivore-induced plant volatiles (HIPVs) from the teosintes and maize. Larval growth and survival were reduced on teosintes relative to maize. Whilst larvae fed on perennial teosinte had lower food intake indices, those on annual teosinte showed lower food utilisation indices relative to maize. The earwig preferred HIPVs emitted by teosintes over those by maize, but it did not discriminate between odours of herbivore-damaged annual and perennial teosinte. The nocturnal HIPV blend from maize contained the lowest total amount of fatty acid derivatives, while it had higher total amounts of terpenes compared to teosintes. Our study shows that the teosintes are better defended than maize in terms of direct and indirect defences; however, the perennial teosinte have stronger direct defences against the fall armyworm than the annual teosinte. [ABSTRACT FROM AUTHOR]

Zoophytophagous plant bugs feed on plant tissue as a source of water and nutrients, besides feeding on prey. By phytophagy, mirid predators activate plant defense responses through different pathways, resulting, among others, in the release of herbivore‐induced plant volatiles (HIPVs). These compounds could repel herbivores and attract parasitoids and predators, and synthetic versions could potentially be used in biological control. Nevertheless, little is known about the influence of synthetic volatiles on mirid attraction. Using Y‐tube olfactometer trials, we evaluated the responses of Nesidiocoris tenuis (Reuter), Macrolophus pygmaeus (Rambur), and Dicyphus bolivari Lindberg (Hemiptera: Miridae), important natural enemies used to control various greenhouse pests, to 10 synthetic versions of HIPVs released from tomato (Solanum lycopersicum L., Solanaceae) plants induced by N. tenuis and M. pygmaeus. Nesidiocoris tenuis responded to five of the 10 HIPVs, whereas M. pygmaeus and D. bolivari responded to four of the 10 HIPVs. Two green leaf volatiles, (Z)‐3‐hexenyl propanoate and (Z)‐3‐hexenyl acetate, and the ester methyl salicylate (MeSA) were attractive to all three mirid predator species. Our results demonstrate that the volatiles released by tomato plants activated by N. tenuis and M. pygmaeus phytophagy are attractive to their conspecifics and also to D. bolivari. Further studies should evaluate the potential of these compounds to attract predatory mirids in the field. [ABSTRACT FROM AUTHOR]