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PubMed1990

Chemistry of male dominance in the house mouse, Mus domesticus.

Two terpenic constituents, E,E,-alpha-farnesene and E-beta-farnesene, were found to be elevated in dominant male urine when compared to subordinate or control males. These two urinary compounds were absent in the bladder urine of males; however, they were the most prominent constituents of the perputial gland's aliquots. The results of a two-choice preference test, conducted on ICR/Alb subordinate males, gave a strong indication that these two terpenic constituents introduced into the previously attractive stimulus significantly discouraged prolonged investigations by male mice. The compounds, whether present in the urine matrix or water, rendered the stimulus with a quality behaviorally similar to the urine of dominant males. It appears that they may be synonymous with the previously described aversion signal produced by dominant males. We suggest that these compounds may play a wide-ranging role in the territorial marking behavior of male mice.

Animals↗

PubMed2005

Formulation of microemulsion systems for transdermal delivery of aceclofenac.

An ONW microemulsion system was developed to enhance the skin permeability of aceclofenac. Of the oils studied, Labrafil M 1944 CS was chosen as the oil phase of the microemulson, as it showed a good solubilizing capacity. Pseudo-ternary phase diagrams were constructed to obtain the concentration range of oil, surfactant, Cremophor ELP, and co-surfactant, ethanol, for micoemulsion formation. Eight different formulations with various values of oil of 6-30%, water of 0-80%, and the mixture of surfactant and co-surfactant (at the ratio of 2) of 14-70%. The in vitro transdermal permeability of aceclofenac from the microemulsions was evaluated using Franz diffusion cells mounted with rat skin. The level of aceclofenac permeated was analyzed by HPLC and the droplet size of the microemulsions was characterized using a Zetasizer Nano-ZS. Terpenes were added to the microemulsions at a level of 5%, and their effects on the skin permeation of aceclofenac were investigated. The mean diameters of the microemulsions ranged between approximately 10-100 nm, and the skin permeability of the aceclofenac incorporated into the microemulsion systems was 5-fold higher than that of the ethanol vehicle. Of the various terpenes added, limonene had the best enhancing ability. These results indicate that the microemulsion system studied is a promising tool for the percutaneous delivery of aceclofenac.

Administration, Cutaneous↗

PubMed2002

[Allergic reaction after contact with Hura crepitans (sandbox tree)].

We describe a 36-year-old female patient with angioedema-like swellings and rhinoconjunctivitis for 1 year occurring exclusively at her home. The clinical history revealed no correlation with foods, food additives, drugs, or aeroallergens. The complaints always started immediately after contact with the sandbox tree (Hura crepitans) placed in her apartment. Scratch testing resulted in a two-fold positive reaction towards leaves and stem, while five controls remained negative. Thus we suggest the reaction of the patient to be allergic in nature. Hura crepitans belongs to the family of Euphorbiaceae, whose largest genera are Euphorbia and Croton. The toxic reactions to the milky sap, the so-called latex, of these plants are caused by ingredients such as phorbol esters, croton oil, lectins, and terpens. Various terpens are also well known as allergens. Phytotoxic and phytoallergic reactions are growing increasingly important and should therefore be included in the differential diagnosis in dermatology.

Adult↗

PubMed1999

Inflammation markers in nasal lavage, and nasal symptoms in relation to relocation to a newly painted building: a longitudinal study.

INTRODUCTION: There is a need to evaluate possible health effects of ventilation improvements and emissions from new buildings, in longitudinal studies. New methods to study biological effects on the eyes and upper airways are now available. MATERIAL AND METHODS: A longitudinal study was performed on 83 trained social workers in two offices in Uppsala, Sweden. The exposed group (n = 57) moved to a newly redecorated building nearby. Low emitting building material had been used, including a new type of solvent-free water-based paint. The control group (n = 26) worked in the same office during the study period (November 1995 to February 1996). Hygiene management was carried out in both offices, at the beginning and the end of the investigation. Tear film stability (BUT) was measured. Nasal patency was measured by acoustic rhinometry, and eosinophilic cationic protein (ECP), myeloperoxidase (MPO), lysozyme and albumin were analyzed in nasal lavage fluid (NAL). RESULTS: The relocation resulted in an increase in the personal outdoor airflow rate from 11 to 22 l/s. Indoor concentrations of terpenes were higher in the new building, and powdering of the new linoleum floor was observed. Measurements showed low levels of volatile organic compounds (VOC), formaldehyde, carbon dioxide (CO(2)), nitrogen dioxide, respirable dust, and microorganisms in the air of all buildings. The move resulted in an increased nasal patency and an increase of ECP and lysozyme in NAL, after adjusting for changes in the control group. No changes were observed for nasal or ocular symptoms. A seasonal effect, with a decrease of ECP, was observed in the control group. CONCLUSSION A well-ventilated office building can be redecorated without any major ocular or nasal effects, or measurable increase of indoor air pollution if low-emitting building materials are selected. In agreement with previous evidence, the improved ventilation flow may explain the increase of nasal patency. The increase of ECP and lysozyme in NAL suggested an inflammatory effect in the new building. Since this building had increased ventilation flow, increased concentrations of terpenes, and powdering from the polish on the new linoleum floor, identification of causative agents was difficult. The hygiene measures did not give any evidence that emissions from the new type of solvent-free water-based paints or building dampness were responsible for the observed nasal effects. Considering the higher emissions of VOC reported from older types of water-based latex paints and solvent-based wall paints, the new type of solvent-free water-based paint seems to be a good choice from the hygiene point of view.

Adult↗

PubMed2004

Cloning and functional expression of an ( E, E)-alpha-farnesene synthase cDNA from peel tissue of apple fruit.

Increased production of terpenes and many other aroma-related volatiles occurs with the onset of ripening in apple ( Malus domestica Borkh.) fruit. The gaseous plant hormone ethylene plays a key role in the induction of volatile synthesis, but the mechanism is not yet understood. Using a degenerate primer based on a short conserved sequence shared by several sesquiterpene synthases, reverse transcription-polymerase chain reaction with RNA isolated from peel tissue of 'Law Rome' apples yielded an approx. 800-bp gene fragment. This was used to screen a cDNA library generated from the peel tissue mRNA. A full-length terpene synthase (TS) cDNA 1,931 nucleotides long was isolated. The 1,728-bp open reading frame encodes a protein 576 amino acids long with a molecular mass of 66 kDa. Sequence analysis of the apple TS showed it to be most similar to several monoterpene synthases. Oddly, the TS includes an RR(X(8))W motif near the N-terminus that is common among monoterpene synthases but it lacks the plastid transit peptide sequence typically associated with genes of that group. Expression of the apple TS gene in Escherichia coli gave myc-epitope-tagged and untagged proteins estimated at approx. 68 and approx. 66 kDa, respectively. In assays of sesquiterpene synthase activity, with farnesyl diphosphate as substrate, the untagged bacterially expressed TS gene product synthesized ( E, E)-alpha-farnesene almost exclusively. In monoterpene synthase assays, with geranyl diphosphate as substrate, the untagged apple TS produced only ( E)-beta-ocimene, albeit at much reduced levels. Addition of a C-terminal myc tag appeared to completely prevent production of soluble protein under all of the expression conditions tested. This is the first report of an ( E, E)-alpha-farnesene synthase gene ( AFS1; GenBank accession number AY182241) from a flowering plant. RNA gel blots showed that AFS1 transcript increased about 4-fold in peel tissue of apple fruit during the first 4 weeks of storage at 0.5 degrees C. In contrast, when fruit were treated at harvest with 1-methylcyclopropene, a blocker of ethylene action, AFS1 mRNA declined sharply over the initial 4 weeks of cold storage, and fell to nearly undetectable levels by 8 weeks.

Alkyl and Aryl Transferases↗

PubMed2005

Point mutation of (+)-germacrene A synthase from Ixeris dentata.

Sesquiterpene cyclases catalyze the conversion of common precursor, farnesyl pyrophosphate, into various terpene backbones. X-ray crystallography of tobacco epi-aristolochene synthase has previously proposed a cyclization mechanism wherein the allylic carbocation intermediate is stabilized by the main chain carbonyl oxygens of three consecutive threonine residues. Alignment of amino acid sequences of plant terpene cyclases shows that the first position of the triad is almost invariably threonine or serine. To probe the carbocation-stabilizing role, the amino acid residues of the 433TSA435 triad in (+)-germacrene A synthase from Ixeris dentata were altered by site-directed mutagenesis. Enzyme kinetic measurements of the mutants and GC/MS analysis of the enzyme reaction products indicate that mutations of the triad decreased enzyme catalysis rather than substrate binding but did not affect its structural rearrangement in the catalytic mechanism. This is the first report that the hydroxyl group of threonine at the first position of the triad is required for the cyclase activity.

Alkyl and Aryl Transferases↗

PubMed2005

Isolation and characterization of allelopathic volatiles from mugwort (Artemisia vulgaris).

Several volatile allelochemicals were identified and characterized from fresh leaf tissue of three distinct populations of the invasive perennial weed, mugwort (Artemisia vulgaris). A unique bioassay was used to demonstrate the release of volatile allelochemicals from leaf tissues. Leaf volatiles were trapped and analyzed via gas chromatography coupled with mass spectrometry. Some of the components identified were terpenes, including camphor, eucalyptol, alpha-pinene, and beta-pinene. Those commercially available were tested individually to determine their phytotoxicity. Concentrations of detectable volatiles differed in both absolute and relative proportions among the mugwort populations. The three mugwort populations consisted of a taller, highly branched population (ITH-1); a shorter, lesser-branched population (ITH-2) (both grown from rhizome fragments from managed landscapes); and a population grown from seed with lobed leaves (VT). Considerable interspecific variation existed in leaf morphology and leaf surface chemistry. Bioassays revealed that none of the individual monoterpenes could account for the observed phytotoxicity imparted by total leaf volatiles, suggesting a synergistic effect or activity of a component not tested. Despite inability to detect a single dominant phytotoxic compound, decreases in total terpene concentration with increase in leaf age correlated with decreases in phytotoxicity. The presence of bioactive terpenoids in leaf surface chemistry of younger mugwort tissue suggests a potential role for terpenoids in mugwort establishment and proliferation in introduced habitats.

Artemisia↗

PubMed2006

Resource availability and quality influence patterns of diet mixing by sheep.

In grazing systems, forage availability is a function of herbivore density, which can influence an animal's ability to be selective. In turn, the influence of food availability on selectivity has the potential to influence plant biodiversity. We hypothesized that the ability of herbivores to mix toxin-containing foods in their diets is a function of the availability of nontoxic foods and the nutritional characteristics of the toxin-containing foods. We evaluated this hypothesis in two trials simulating different diet qualities (high-quality foods in trial 1, low-quality foods in trial 2). Within each trial, the four treatment groups were offered with different amounts of nutritious, familiar foods-10, 30, 50, and 70% of ad libitum intake-but were offered with ad libitum access to toxin-containing foods. Each lamb was presented with five foods, including three toxin-containing unfamiliar foods (terpenes, tannins, and oxalates) and two nutritious familiar foods (alfalfa and barley). In trial 1, as the availability of nutritious familiar foods decreased, animals ate more of all three toxin-containing foods. As the availability of nutritious alternatives increased, the pattern of selection shifted from terpenes to tannins and oxalates. In trial 2, animals also ate more toxins as the availability of nutritious alternatives decreased, but their pattern of diet mixing changed. Low availability of nutritious alternatives resulted in the animals eating more oxalates. During preference tests when all five foods were offered ad libitum, animals fed with 10, 30, 50, and 70% of ad libitum intake from trial 1 ate 49, 47, 41, and 38% of the three toxin-containing foods, respectively. The lower diet quality in trial 2 affected intake of the toxin-containing foods such that animals fed with 10, 30, 50, and 70% of ad libitum intake ate 37, 36, 29, and 27%, respectively, of the three toxin-containing foods. Thus, the quality of toxin-containing foods and the availability of nutritious alternatives interacted to modify the pattern of diet mixing by lambs.

Animals↗

PubMed1993

Characterization of cannabidiol-mediated cytochrome P450 inactivation.

Cannibidiol (CBD) has been shown to impair hepatic drug metabolism in several animal species and to markedly inhibit mouse hepatic microsomal delta 1-tetrahydrocannabinol (THC) metabolism by inactivating specific cytochrome P450s (P450) belonging to the 2C and 3A subfamilies. Elucidation of the mechanism of CBD-mediated P450 inhibition would be clinically very important for predicting its effect on metabolism of THC and the many other clinically important drugs known to be metabolized by P450s 2C and 3A. CBD-mediated inactivation of mouse hepatic microsomal P450s did not decrease hepatic microsomal heme content. However, [14C]CBD was found covalently bound to microsomal protein in an approximately equimolar ratio to P450 loss. Immunoprecipitation of microsomal protein with antibodies raised against either P450 2C or 3A revealed that approximately equal amounts of [14C]-CBD were bound to each of these P450s after CBD-mediated inactivation. Furthermore, this specific P450 binding was equivalent to P450 loss and accounted for nearly all of the microsomal [14C]CBD irreversible binding. Although > 80% of the enzyme activities attributed to P450s 2C and 3A were inactivated by CBD at the anticonvulsant dose of 120 mg/kg, P450 2C was approximately 3-fold more sensitive than P450 3A at the lower CBD doses tested. CBD analogs were synthesized in order to elucidate the chemical pathways for CBD-mediated P450 inactivation in vivo. Oxidations at allylic carbon positions or saturation of either the exocyclic double bond or both double bonds of the terpene moiety did not markedly affect the inhibitory properties of the analogs. Methylation of both phenolic groups of the resorcinol moiety completely blocked the P450-inhibitory properties of this analog, revealing the involvement of a free hydroxyl group in the inactivation process. Rotation of the resorcinol moiety in abnormal-CBD did not impair the inhibitory properties of the analog, suggesting that the position of the hydroxyl group relative to the terpene ring is unimportant. Further studies are required to fully understand the chemical basis of CBD-mediated P450 inactivation.

Animals↗

PubMed1976

Toxic effect of alantolactone and dihydroalantolactone in in vitro cultures of leukocytes.

Alantolactone, an allergenic sesquiterpene lactone, is toxic to leukocytes in in vitro cultures. Cell (1 X 10(6) cells/ml of culture) stimulation by pokeweed mitogen (PWM) decreases with increasing amounts of terpene. A concentration of 1 mug/ml of culture decreases stimulation by 50%. The reduced terpene, dihydro-11,13-alantolactone (DHA) is also toxic. A concentration of 1.7 mug/ml of culture of DHA brings about a 50% decrease in stimulation. Both compounds affect cell viability as measured by dye exclusion. It is suggested that the toxicity of alantolactone is not due to the presence of the alpha-methylene group conjugated to the carbonyl function of the gamma-lactone system.

Benzofurans↗

PubMed1991

Dye-ligand and immobilized metal ion interaction chromatography for the purification of enzymes of prenyl pyrophosphate metabolism.

Dye-ligand and immobilized metal ion interaction chromatography were shown to be efficient techniques for the rapid batchwise fractionation, from crude plant extracts, of a series of enzymes of prenyl pyrophosphate metabolism. Isopentenyl pyrophosphate isomerase, two prenyltransferases, and a number of terpene cyclases (synthases) were readily adsorbed to Matrex Gel Red A (a dimeric triazine dye coupled to cross-linked agarose beads), and desorbed in good yield with relatively high concentrations of KCl and increasing pH. Although all of these enzymes exhibit the common feature of employing a pyrophosphorylated substrate, selective elution could not be achieved with substrate or substrate analogues bearing a pyrophosphate function. Nor could the strong binding of these enzymes to triazine dyes be attributed solely to metal ion interactions or to hydrophobic effects. In a similar way, the isomerase, the prenyltransferases, and all of the terpene cyclases bound to a column of iminodiacetate-immobilized Ni(II) and were desorbed in relatively high fold purity with 15 mM imidazole. Although all of these enzymes bear accessible histidine residues, the interactions with the chelated metal ion were not sufficiently different to permit selective enzyme desorbtion by imidazole gradient elution. However, the use of columns charged with Zn(II) or Co(II) did allow some separation of the different cyclase and transferase types. While empirical in nature, these techniques offer simple, effective, and high-capacity methods for the preliminary concentration and purification of a group of enzymes that utilize prenyl pyrophosphate intermediates of isoprenoid biosynthesis.

Chromatography, Affinity↗

PubMed2006

Redesign of a central enzyme in alkaloid biosynthesis.

Plant alkaloids exhibit a diverse array of structures and pharmaceutical activities, though metabolic engineering efforts in these eukaryotic pathways have been limited. Strictosidine synthase (STR) is the first committed step in the biosynthesis of over two thousand terpene indole alkaloids. We describe a rational redesign of the STR binding pocket to selectively accommodate secologanin substrate analogs. The mutant is selective for a substrate that can be chemoselectively derivatized. Evidence that this substrate can be processed by later steps of the terpene indole alkaloid pathway is provided. The work demonstrates that the central enzyme of this alkaloid pathway can be redesigned and that the pathway can turn over the unnatural intermediate that is generated. Modulation of the substrate specificity of enzymes of this complex pathway is therefore likely to enable metabolic engineering efforts of these alkaloids.

Carbon-Nitrogen Lyases↗

PubMed2006

Characterization and quantification of the hydrocarbons fraction of the subcutaneous fresh fat of Iberian pig by off-line combination of high performance liquid chromatography and gas chromatography.

Hydrocarbons in fresh subcutaneous fat of Iberian pig have been analyzed by GC-MS after fractionation of the unsaponifiable fraction with a new off-line combination of HPLC and GC method. The new method proposed improves the recovery and simultaneous quantification of terpenic hydrocarbons in comparison to the traditional LC method. When necessary and for identification purposes, selective ion monitoring (SIM) was used as acquisition mode in GC-MS. To determine the position of the double bonds in the unsaturated hydrocarbon chain the dimethyl disulfide derivatives (DMDS) were obtained. To elucidate the structure of the branched 1-alkenes the hydrocarbon fraction was submitted to hydrogenation. Thirty-five compounds have been identified, including n-alkanes, n-alkenes, branched (n-1,n-2-dimethyl-1-alkenes) and terpenic hydrocarbons, being the most abundant n-alkenes and n-alkanes of even chain of n-C12-n-C26. Besides the hydrocarbons already described in bibliography, a new diterpenic hydrocarbon, ent-kaurene, have been identified for the first time. The compound reported as Neophytadiene by other authors, has been identified as a 20 atoms hydrocarbon with two double bonds, the 7,11,15-trimethyl-heptadeca-1,4-diene.

Animals↗

PubMed2006

Monoterpene and sesquiterpene hydrocarbons of virgin olive oil by headspace solid-phase microextraction coupled to gas chromatography/mass spectrometry.

In the present article, a headspace solid-phase microextraction method coupled to GC/MS was developed and applied for the simultaneous determination of mono- and sesquiterpenic hydrocarbons in virgin olive oils of different olive variety and geographical origin. Analysis of various oils resulted in the simultaneous detection of 15 monoterpenes and 30 sesquiterpenes. Some of these hydrocarbons were previously reported to be constituents of virgin olive oil terpenoid fraction, although we also detected some terpenic hydrocarbons that have not previously been documented as present in virgin olive oil. Significant differences were detected in the proportion of terpenic compounds in oils obtained from different olive varieties grown in different geographical areas. The monoterpene, and particularly the sesquiterpene composition of olive oil may be used to distinguish samples from different cultivar and geographical areas.

Gas Chromatography-Mass Spectrometry↗

PubMed2004

Surface activity of thymol: implications for an eventual pharmacological activity.

In the present work, we studied the ability of thymol to affect the organization of model membranes and the activity of an intrinsic membrane protein, the GABA(A) receptor (GABA(A)-R). In this last aspect, we tried to elucidate if the action mechanism of this terpene at the molecular level, involves its binding to the receptor protein, changes in the organization of the receptor molecular environment, or both. The self-aggregation of thymol in water with a critical micellar concentration approximately = 4 microM and its ability to penetrate in monomolecular layers of soybean phosphatidylcholine (sPC) at the air-water interface, even at surface pressures above the equilibrium, lateral pressure of natural bilayers were demonstrated. Thymol affected the self-aggregation of Triton X-100 and the topology of sPC vesicles. It also increased the polarity of the membrane environment sensed by the electrochromic dye merocyanine. A dipolar moment of 1.341 Debye was calculated from its energy-minimized structure. Its effect on the binding of [3H]-flunitrazepam ([3H]-FNZ) to chick brain synaptosomal membranes changed qualitatively from a tendency to the inhibition to a clear activatory regime, up on changing the phase state of the terpene (from a monomeric to a self-aggregated state). Above its CMC, thymol increased the affinity of the binding of [3H]-FNZ (K(d-control)= 2.9, K(d-thymol)= 1.7 nM) without changing the receptor density (B(max-control)= 910, B(max-thymol)= 895 fmol/mg protein). The activatory effect of thymol on the binding of [ [3H]-FNZ was observed even in the presence of the allosteric activator gamma-aminobutyric acid (GABA) at a concentration of maximal activity, and was blocked by the GABA antagonist bicuculline. Changes in the dipolar arrangement and in the molecular packing of GABA(A)-R environment are discussed as possible mediators of the action mechanism of thymol.

Air↗

PubMed2006

Cloning and characterization of the erg1 gene of Trichoderma harzianum: effect of the erg1 silencing on ergosterol biosynthesis and resistance to terbinafine.

Trichoderma species are commonly used as biocontrol agents of different plant-pathogenic fungi. Terpene compounds are involved in the biocontrol process due to their antifungal properties (e.g., ergokonins and viridins) but additionally their structural function in the cell membranes (ergosterol) is essential. We report here the characterization of the T. harzianum erg1 gene, encoding a squalene epoxidase, a key enzyme in the biosynthesis of triterpene derivatives such as ergosterol. In T. harzianum the partial silencing of the erg1 gene gave rise to transformants with a higher level of sensitivity to terbinafine, an antifungal compound that acts specifically over the squalene epoxidase activity. In addition, these silenced transformants produced lower levels of ergosterol than the wild type strain. Finally, the silencing of the erg1 gene resulted in an increase in the expression level of the erg7 gene that encodes the oxidosqualene lanosterol-cyclase, another enzyme of the terpene biosynthesis pathway.

Antifungal Agents↗

PubMed2005

Biosynthesis of mono- and sesquiterpenes in carrot roots and leaves (Daucus carota L.): metabolic cross talk of cytosolic mevalonate and plastidial methylerythritol phosphate pathways.

The biosynthesis of the monoterpenes terpinolene and myrcene and the sesquiterpene beta-caryophyllene in roots and leaves of two carrot varieties (Daucus carota L. cultivars Bolero and Kazan) were investigated by in vivo feeding experiments with [5,5-2H2]-mevalonic acid lactone (d2-MVL) and [5,5-2H2]-1-deoxy-D-xylulose (d2-DOX). The volatiles of the tissues were extracted by stir bar sorptive extraction and analyzed using thermal desorption-multidimensional gas chromatography-mass spectrometry. The experiments demonstrate independent de novo-biosynthesis of terpenoids in carrot roots and in carrot leaves. In both plant tissues monoterpenes are biosynthesized exclusively via the 1-deoxy-D-xylulose/2-C-methyl-D-erythritol-4-phosphate (DOXP/MEP) pathway, whereas sesquiterpenes are generated by the classical mevalonic acid pathway as well as by the DOXP/MEP route. A more detailed investigation of carrot root tissues revealed that the biosynthesis of terpenes is mainly localized in the phloem. Nevertheless, in xylem a de novo-biosynthesis of terpenes was detectable as well, even in the absence of oil ducts in this tissue.

Cytosol↗

PubMed2005

How rainfall, relative humidity and temperature influence volatile emissions from apple trees in situ.

Headspace volatiles from apple-bearing twigs were collected in the field with a Radiello sampler during three different diurnal periods over the complete fruit growing season. Analyses by thermal desorption-GC-MS identified a total of 62 compounds in changing quantities, including the terpenoids alpha-pinene, camphene, beta-pinene, limonene, beta-caryophyllene and (E,E)-alpha-farnesene, the aldehydes (E)-2-hexenal, benzaldehyde and nonanal, and the alcohol (Z)-3-hexen-1-ol. The variations in emission of these plant odours were statistically related to temperature, humidity and rainfall in the field. Remarkably, rainfall had a significant positive influence on changes in volatile release during all three diurnal periods, and further factors of significance were temperature and relative humidity around noon, relative humidity in the late afternoon, and temperature and relative humidity during the night. Rainfall was associated consistently with an increase in the late afternoon in terpene and aldehyde volatiles with a known repellent effect on the codling moth, one of the key pests of apple fruit. During the summer of 2003, a season characterized by below-average rainfall, some postulated effects of drought on trees were tested by establishing correlations with rainfall. Emissions of the wood terpenes alpha-pinene, beta-pinene and limonene were negatively correlated with rainfall. Another monoterpene, camphene, was only detected in this summer but not in the previous years, and its emissions were negatively correlated with rainfall, further supporting the theory that drought can result in higher formation of secondary metabolites. Finally, the two green leaf volatiles (E)-2-hexenal and (Z)-3-hexen-1-ol were negatively correlated with rainfall, coinciding well with the expectation that water deficit stress increases activity of lipoxygenase. To our knowledge, this work represents the first empirical study concerning the influence of abiotic factors on volatile emissions from apple trees in situ.

Climate↗