Sesquiterpene Emissions Research Articles

Genotypic Variation and Phenotypic Plasticity in Gene Expression and Emissions of Herbivore-Induced Volatiles, and their Potential Tritrophic Implications, in Cranberries.

Herbivorous insects are important problems in cranberry (Vaccinium macrocarpon Ait.) production. The use of chemical pesticides is common practice, but beneficial insects such as natural enemies of herbivores (e.g. predators and parasitoids) could be affected as well. Therefore, we studied the defensive mechanisms that cranberry plants use to combat pests, focusing on herbivore-induced plant volatiles (HIPVs), which can be used to recruit predators and parasitoids foraging for prey or hosts. Then, we used synthetic HIPVs to test the attraction of natural enemies. In a greenhouse, we assessed nine cranberry genotypes for expression of genes involved in HIPV biosynthesis and/or emission of HIPVs. In an experimental field, we assessed whether baiting traps with individual or combinations of HIPVs increased attractiveness to natural enemies. The results showed that different cranberry genotypes vary in their emission of monoterpenes and sesquiterpenes but not in their expression of two genes associated with terpene biosynthesis, α-humulene/β-caryophyllene synthase and (3S,6E)-nerolidol/R-linalool synthase. Induction with methyl jasmonate or herbivore (gypsy moth, Lymantria dispar L.) feeding increased the expression of these genes and emission of HIPVs. The HIPV methyl salicylate (MeSA), alone or in combination with other HIPVs, increased syrphid attraction by 6-fold in the field, while (Z)-3-hexenyl acetate and MeSA repelled ladybeetles and megaspilids, respectively. Linalool and β-caryophyllene elicited no behavioral responses of natural enemies. Elucidating the mechanisms of pest resistance, as well as experimentally augmenting plant defenses such as HIPVs, may contribute to the development of more sustainable pest management practices in crops, including cranberries.

New Perspectives on CO2, Temperature, and Light Effects on BVOC Emissions Using Online Measurements by PTR-MS and Cavity Ring-Down Spectroscopy.

Volatile organic compounds (VOC) play important roles in atmospheric chemistry, plant ecology, and physiology, and biogenic VOC (BVOC) emitted by plants is the largest VOC source. Our knowledge about how environmental drivers (e.g., carbon, light, and temperature) may regulate BVOC emissions is limited because they are often not controlled. We combined a greenhouse facility to manipulate atmospheric CO2 ([CO2]) with proton-transfer-reaction mass spectrometry (PTR-MS) and cavity ring-down spectroscopy to investigate the regulation of BVOC in Norway spruce. Our results indicate a direct relationship between [CO2] and methanol and acetone emissions, and their temperature and light dependencies, possibly related to substrate availability. The composition of monoterpenes stored in needles remained constant, but emissions of mono-(linalool) and sesquiterpenes (β-farnesene) increased at lower [CO2], with the effects being most pronounced at the highest air temperature. Pulse-labeling suggested an immediate incorporation of recently assimilated carbon into acetone, mono- and sesquiterpene emissions even under 50 ppm [CO2]. Our results provide new perspectives on CO2, temperature and light effects on BVOC emissions, in particular how they depend on stored pools and recent photosynthetic products. Future studies using smaller but more seedlings may allow sufficient replication to examine the physiological mechanisms behind the BVOC responses.

Strong sesquiterpene emissions from Amazonian soils

The Amazon rainforest is the world’s largest source of reactive volatile isoprenoids to the atmosphere. It is generally assumed that these emissions are products of photosynthetically driven secondary metabolism and released from the rainforest canopy from where they influence the oxidative capacity of the atmosphere. However, recent measurements indicate that further sources of volatiles are present. Here we show that soil microorganisms are a strong, unaccounted source of highly reactive and previously unreported sesquiterpenes (C15H24; SQT). The emission rate and chemical speciation of soil SQTs were determined as a function of soil moisture, oxygen, and rRNA transcript abundance in the laboratory. Based on these results, a model was developed to predict soil–atmosphere SQT fluxes. It was found SQT emissions from a Terra Firme soil in the dry season were in comparable magnitude to current global model canopy emissions, establishing an important ecological connection between soil microbes and atmospherically relevant SQTs.

Volatile organic compounds (VOC) variation in Croton floribundus (L.) Spreng. related to environmental conditions and ozone concentration in an urban forest of the city of São Paulo, São Paulo State, Brazil

ABSTRACT Volatile organic compounds (VOC) are emitted by vegetation in response to different kinds of stress, such as herbivory, environmental conditions and air pollutants. The aim of this study was to identify the VOC emitted by seedlings of Croton floribundus (L.) Spreng. exposed to a polluted environment and analyze the relationship among classes of compounds emitted, ozone levels and changes in climate conditions. Two exposures were carried out, one in winter (June to August 2012) and another in summer (January to April 2013), in the Parque Estadual das Fontes do Ipiranga, city of São Paulo, São Paulo State, Brazil. We identified 26 compounds that are grouped into oxygenates, aromatics, monoterpenes and sesquiterpenes. The emission of sesquiterpenes was inhibited in summer, while those of the oxygenated and aromatic compounds were induced. The emission of volatiles was correlated to ozone levels (AOT 40). Our results suggest that the levels of atmospheric ozone detected in the summer can increase the induction of oxygenates and reduce the emission of monoterpenes in C. floribundus plants.

Seasonal cycles of secondary organic aerosol tracers in rural Guangzhou, Southern China: The importance of atmospheric oxidants

Thirteen secondary organic aerosol (SOA) tracers of isoprene (SOAI), monoterpenes (SOAM), sesquiterpenes (SOAS) and aromatics (SOAA) in fine particulate matter (PM2.5) were measured at a Pearl River Delta (PRD) regional site for one year. The characteristics including their seasonal cycles and the factors influencing their formation in this region were studied. The seasonal patterns of SOAI, SOAM and SOAS tracers were characterized over three enhancement periods in summer (I), autumn (II) and winter (III), while the elevations of SOAA tracer (i.e., 2,3-dihydroxy-4-oxopentanoic acid, DHOPA) were observed in Periods II and III. We found that SOA formed from different biogenic precursors could be driven by several factors during a one-year seasonal cycle. Isoprene emission controlled SOAI formation throughout the year, while monoterpene and sesquiterpene emissions facilitated SOAM and SOAS formation in summer rather than in other seasons. The influence of atmospheric oxidants (Ox) was found to be an important factor of the formation of SOAM tracers during the enhancement periods in autumn and winter. The formation of SOAS tracer was influenced by the precursor emissions in summer, atmospheric oxidation in autumn and probably also by biomass burning in both summer and winter. In this study, we could not see the strong contribution of biomass burning to DHOPA as suggested by previous studies in this region. Instead, good correlations between observed DHOPA and Ox as well as [NO2][O3] suggest the involvement of both ozone (O3) and nitrogen dioxide (NO2) in the formation of DHOPA. The results showed that regional air pollution may not only increase the emissions of aromatic precursors but also can greatly promote the formation processes.

Effects of a Detailed Vegetation Database on Simulated Meteorological Fields, Biogenic VOC Emissions, and Ambient Pollutant Concentrations over Japan

Regional air quality simulations provide powerful tools for clarifying mechanisms of heavy air pollution and for considering effective strategies for better air quality. This study introduces a new vegetation database for Japan, which could provide inputs for regional meteorological modeling, and estimating emissions of biogenic volatile organic compounds (BVOCs), both of which are essential components of simulations. It includes newly developed emission factors (EFs) of BVOCs for major vegetation types in Japan, based on existing literature. The new database contributes to improved modeling of meteorological fields due to its updated representation of larger urban areas. Using the new vegetation and EF database, lower isoprene and monoterpene, and higher sesquiterpene emissions are estimated for Japan than those derived from previously available default datasets. These slightly reduce the overestimation of ozone concentrations obtained by a regional chemical transport model, whereas their effects on underestimated secondary organic aerosol (SOA) concentrations are marginal. Further work is necessary, not only on BVOC emissions but also the other simulation components, to further improve the modeling of ozone and SOA concentrations in Japan.

Volatile diterpene emission by two Mediterranean Cistaceae shrubs

Mediterranean vegetation emits a wide range of biogenic volatile organic compounds (BVOCs) among which isoprenoids present quantitatively the most important compound class. Here, we investigated the isoprenoid emission from two Mediterranean Cistaceae shrubs, Halimium halimifolium and Cistus ladanifer, under controlled and natural conditions, respectively. For the first time, diurnal emission patterns of the diterpene kaurene were detected in real-time by Proton-Transfer-Reaction-Time-of-Flight-Mass-Spectrometer. Kaurene emissions were strongly variable among H. halimifolium plants, ranging from 0.01 ± 0.003 to 0.06 ± 0.01 nmol m−2 s−1 in low and high emitting individuals, respectively. They were in the same order of magnitude as monoterpene (0.01 ± 0.01 to 0.11 ± 0.04 nmol m−2 s−1) and sesquiterpene (0.01 ± 0.01 to 0.52 nmol m−2 s−1) emission rates. Comparable range and variability was found for C. ladanifer under natural conditions. Labelling with 13C-pyruvate suggested that emitted kaurene was not derived from de novo biosynthesis. The high kaurene content in leaves, the weak relationship with ecophysiological parameters and the tendency of higher emissions with increasing temperatures in the field indicate an emission from storage pools. This study highlights significant emissions of kaurene from two Mediterranean shrub species, indicating that the release of diterpenes into the atmosphere should probably deserve more attention in the future.

Impact of warming, moderate nitrogen addition and bark herbivory on BVOC emissions and growth of Scots pine (Pinus sylvestris L.) seedlings.

The changing climate will expose boreal forests to rising temperatures, increasing soil nitrogen (N) levels and an increasing risk of herbivory. The single and interaction effects of warming (+2 °C increase), moderate N addition (30 kg ha-1 year-1) and bark herbivory by large pine weevil (Hylobius abietis L.) on growth and emissions of biogenic volatile organic compounds (BVOCs) from shoots of Scots pine (Pinus sylvestris L.) seedlings were studied in growth chambers over 175 days. In addition, warming and N addition effects on shoot net photosynthesis (Pn) were measured. Nitrogen addition increased both shoot and root dry weights, whereas warming, in combination with herbivory, reduced stem height growth. Warming together with N addition increased current-year shoot Pn, whereas N effects on previous-year shoot Pn were variable over time. Warming decreased non-oxygenated monoterpene (MT) emissions in June and increased them in July. Of individual MT compounds, α-pinene, δ-3-carene, γ-terpinene and terpinolene were among the most frequently responsive compounds in warming treatments in the May-July period. Sesquiterpene emissions were observed only from warming treatments in July. Moderate N addition increased oxygenated monoterpenes in May, and MTs in June and September. However, N addition effect on MTs in June was clearer without warming than with warming. Bark herbivory tended to increase MT emissions in combination with warming and N addition 3 weeks after the damage caused by weevils. Of individual compounds in other BVOC blends, herbivory increased the emissions of methyl-benzene, benzene and hexanal in July. Hence, though both warming and N addition have a potential to change BVOC emissions from Scots pines, the N effect may also be partly cancelled by warming. Furthermore, herbivory pressure in combination with climate warming and N addition may, at least periodically, increase BVOC release to the atmosphere from young Scots pine seedlings.

A laboratory high-throughput glass chamber using dynamic headspace TD-GC/MS method for the analysis of whole Brassica napus L. plantlet volatiles under cadmium-related abiotic stress.

IntroductionThe dynamic headspace sampling technique using thermal desorption, gas chromatography‐mass spectrometry (TD‐GC/MS) is a powerful method for analysing plant emissions of volatile organic compounds (VOCs), and experiments performed in sterile and controlled conditions can be useful for VOC metabolism investigations.ObjectiveThe main purpose of this study was to set up a laboratory high‐throughput glass chamber for whole plant volatiles analysis. Brassica napus L. plantlets were tested with the developed system to better understand the relationship between low emission of induced terpene and cadmium (Cd)‐related abiotic stress.MethodologyVOCs emitted by 28‐day‐old Brassica napus L. plantlets cultivated in vitro were trapped with our device using adsorbent cartridges that were desorbed with a thermal desorption unit before cryofocusing with a cooled injection system and programmable temperature vaporising inlet into an HP‐5 ms GC column. Terpene detection and quantitation from chromatogram profiles were acquired using selected ion monitoring (SIM) mode during full scan analysis and mass spectra were obtained with a quadrupole‐type mass spectrometer.ResultsThe new trapping method produced reliable qualitative profiles of oilseed rape VOCs. Typical emissions of monoterpenes (myrcene, limonene) and sesquiterpenes (β‐elemene, (E,E)‐α‐farnesene) were found for the different concentrations tested. One‐way analysis of variance for quantitative results of (E,E)‐α‐farnesene emission rates showed a Cd concentration effect.ConclusionThis inexpensive glass chamber has potential for wide application in laboratory sterile approach and replicated research. Moreover, the non‐invasive dynamic sampling technique could also be used to analyse volatiles under both abiotic and biotic stresses.

Terpene Composition Complexity Controls Secondary Organic Aerosol Yields from Scots Pine Volatile Emissions

Secondary organic aerosol (SOA) impact climate by scattering and absorbing radiation and contributing to cloud formation. SOA models are based on studies of simplified chemical systems that do not account for the chemical complexity in the atmosphere. This study investigated SOA formation from a mixture of real Scots pine (Pinus sylvestris) emissions including a variety of monoterpenes and sesquiterpenes. SOA generation was characterized from different combinations of volatile compounds as the plant emissions were altered with an herbivore stress treatment. During active herbivore feeding, monoterpene and sesquiterpene emissions increased, but SOA mass yields decreased after accounting for absorption effects. SOA mass yields were controlled by sesquiterpene emissions in healthy plants. In contrast, SOA mass yields from stressed plant emissions were controlled by the specific blend of monoterpene emissions. Conservative estimates using a box model approach showed a 1.5- to 2.3-fold aerosol enhancement when the terpene complexity was taken into account. This enhancement was relative to the commonly used model monoterpene, “α-pinene”. These results suggest that simplifying terpene complexity in SOA models could lead to underpredictions in aerosol mass loading.

Ozone-triggered surface uptake and stress volatile emissions in Nicotiana tabacum 'Wisconsin'.

Ozone is a strong oxidant and a key stress elicitor. The immediate and longer term impacts of ozone are poorly understood in species with emission of both de novo synthesized and stored volatiles, such a tobacco (Nicotiana tabacum), which has terpene-containing glandular trichomes on the leaf surface. In this study, we exposed N. tabacum 'Wisconsin' leaves to acute ozone doses of 0 (control), 400, 600, 800, and 1000 ppb for 30 min and studied the effects of ozone exposure on ozone uptake, gas-exchange characteristics, and emissions of lipoxygenase pathway volatiles, monoterpenes, and sesquiterpenes. Foliage emissions of lipoxygenase pathway volatiles were quantitatively related to the severity of ozone exposure, but the stress dose vs. emission relationship was weaker for terpenoids. Analysis of leaf terpene content and composition indicated that several monoterpenes and sesquiterpenes were not stored in leaves and were synthesized de novo upon ozone exposure. The highest degree of elicitation for each compound was observed immediately after ozone treatment and it declined considerably during recovery. Leaf ozone uptake was dominated by non-stomatal deposition, and the emissions of total lipoxygenase pathway volatiles and mono- and sesquiterpenes were positively correlated with non-stomatal ozone deposition. Overall, this study demonstrates remarkably high ozone resistance of the studied tobacco cultivar and indicates that ozone's effects on volatile emissions primarily reflect modifications in the release of stored volatiles and reaction of ozone with the leaf surface structure.

Volatile organic compounds and nitric oxide as responses of a Brazilian tropical species to ozone: the emission profile of young and mature leaves.

The emission profile of volatile organic compounds (VOCs) and nitric oxide (NO) in young and mature leaves of Croton floribundus was assessed in plants exposed to filtered air (FA) and ozone-enriched filtered air (FA+O3). After the period of exposure, leaves were enclosed in polyethylene terephthalate bags and VOCs were collected in young and mature leaves. Both young and mature leaves constitutively emitted the same VOC, but the concentrations were higher in young leaves. O3 exposure induced the emission of sesquiterpenes (mainly β-caryophyllene) known as antioxidant compounds that may scavenge O3. Young leaves were the highest emitters of sesquiterpenes. O3 induced a rapid accumulation of NO in different tissues and leaf developmental stages; this accumulation was marked in palisade and spongy parenchyma cells in young and mature leaves, respectively. O3 altered the levels of the signaling compound methyl salicylate (MeSA). Moreover, our data showed that NO together with VOC emissions, such as geranyl acetate, α-cadiene, trans-farnesol, cis-β-farnesene, and MeSA, participate of plant defense mechanisms against the oxidative damage caused by O3.

Oak gall wasp infections of Quercus robur leaves lead to profound modifications in foliage photosynthetic and volatile emission characteristics.

Oak trees (Quercus) are hosts of diverse gall-inducing parasites, but the effects of gall formation on the physiology and biochemistry on host oak leaves is poorly understood. The influence of infection by four species from two widespread gall wasp genera, Neuroterus (N.anthracinus and N.albipes) and Cynips (C.divisa and C.quercusfolii), on foliage morphology, chemistry, photosynthetic characteristics, constitutive isoprene, and induced volatile emissions in Q. robur was investigated. Leaf dry mass per unit area (MA ), net assimilation rate per area (AA ), stomatal conductance (gs ), and constitutive isoprene emissions decreased with the severity of infection by all gall wasp species. The reduction in AA was mainly determined by reduced MA and to a lower extent by lower content of leaf nitrogen and phosphorus in gall-infected leaves. The emissions of lipoxygenase pathway volatiles increased strongly with increasing infection severity for all 4 species with the strongest emissions in major vein associated species, N.anthracinus. Monoterpene and sesquiterpene emissions were strongly elicited in N.albipes and Cynips species, but not in N.anthracinus. These results provide valuable information for diagnosing oak infections using ambient air volatile fingerprints and for predicting the impacts of infections on photosynthetic productivity and whole tree performance.

Differential regulation of volatile emission from Eucalyptus globulus leaves upon single and combined ozone and wounding treatments through recovery and relationships with ozone uptake

Both ozone and wounding constitute two key abiotic stress factors, but their interactive effects on plant constitutive and stress-elicited volatile (VOC) emissions are poorly understood. Furthermore, the information on time-dependent modifications in VOC release during recovery from a combined stress is very limited. We studied the modifications in photosynthetic characteristics and constitutive and stress-induced volatile emissions in response to single and combined applications of acute ozone (4, 5, and 6ppm) and wounding treatments through recovery (0.5–75h) in a constitutive isoprene and mono- and sesquiterpene emitter Eucalyptus globulus. Overall, the photosynthetic characteristics were surprisingly resistant to all ozone and wounding treatments. Constitutive isoprene emissions were strongly upregulated by ozone and combined ozone and wounding treatments and remained high through recovery phase, but wounding applied alone reduced isoprene emission. All stress treatments enhanced emissions of lipoxygenase pathway volatiles (LOX), mono- and sesquiterpenes, saturated aldehydes (C7-C10), benzenoids, and geranylgeranyl diphosphate (GGDP) pathway volatiles. Once elicited, GGDP volatile, saturated aldehyde and benzenoid emissions remained high through the recovery period. In contrast, LOX emissions, and total mono- and sesquiterpene emissions decreased through recovery period. However, secondary rises in total sesquiterpene emissions at 75h and in total monoterpenes at 25–50h were observed. Overall, acute ozone and wounding treatments synergistically altered gas exchange characteristics and stress volatile emissions. Through the treatments and recovery period, stomatal ozone uptake rate and volatile emission rates were poorly correlated, reflecting possible ozone-scavenging effect of volatiles and thus, reduction of effective ozone dose and elicitation of induced defense by the acute ozone concentrations applied. These results underscore the important role of interactive stresses on both constitutive and induced volatile emission responses.

Methyl jasmonate-induced emission of biogenic volatiles is biphasic in cucumber: a high-resolution analysis of dose dependence.

Methyl jasmonate (MeJA) is a key airborne elicitor activating jasmonate-dependent signaling pathways, including induction of stress-related volatile emissions, but how the magnitude and timing of these emissions scale with MeJA dose is not known. Treatments with exogenous MeJA concentrations ranging from mild (0.2 mM) to lethal (50 mM) were used to investigate quantitative relationships among MeJA dose and the kinetics and magnitude of volatile release in Cucumis sativus by combining high-resolution measurements with a proton-transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) and GC-MS. The results highlighted biphasic kinetics of elicitation of volatiles. The early phase, peaking in 0.1-1 h after the MeJA treatment, was characterized by emissions of lipoxygenase (LOX) pathway volatiles and methanol. In the subsequent phase, starting in 6-12 h and reaching a maximum in 15-25 h after the treatment, secondary emissions of LOX compounds as well as emissions of monoterpenes and sesquiterpenes were elicited. For both phases, the maximum emission rates and total integrated emissions increased with applied MeJA concentration. Furthermore, the rates of induction and decay, and the duration of emission bursts were positively, and the timing of emission maxima were negatively associated with MeJA dose for LOX compounds and terpenoids, except for the duration of the first LOX burst. These results demonstrate major effects of MeJA dose on the kinetics and magnitude of volatile response, underscoring the importance of biotic stress severity in deciphering the downstream events of biological impacts.

Net ecosystem fluxes and composition of biogenic volatile organic compounds over a maize field–interaction of meteorology and phenological stages

AbstractBioenergy crop production is rapidly expanding in Europe, and the potential emissions of biogenic volatile organic compounds (BVOCs) might change the chemical composition of the atmosphere, influencing in turn air quality and regional climate. The environmental impacts of bioenergy crops on air chemistry are difficult to assess due to a lack of accurate field observations. Therefore, we studied BVOC fluxes from a bioenergy maize field in North‐Eastern Germany throughout the entire reproductive growth stage of the plants. Combining automated large chambers and proton transfer reaction mass spectrometry (PTR‐MS), we successfully measured fluxes of the highly reactive hydrocarbons monoterpenes (MTs) and sesquiterpenes (SQTs), together with several other BVOCs, including alcohols, aldehydes, ketones, benzenoids, and fatty acid derivatives. Emissions of MTs and SQTs were relatively high (17.0% and 3.6% of total mean molar BVOC emission, respectively) compared to methanol emissions (17.6%). Seasonal MT and SQT fluxes were clearly associated with the flowering phase, originating mainly from the flowering tissues as shown in additional laboratory experiments. From the observations of CO2 net ecosystem exchange and evapotranspiration rates, we could exclude heat and drought stress‐induced BVOC emissions. Standard emission factors calculated for all compounds, chemical groups, and growth stages, showed that the temperature dependency of volatile terpenoid fluxes decreased distinctively with proceeding development stage. The results indicate that emissions from large‐scale bioenergy maize fields should be better differentiated and considered in regional estimates of aerosol formation. For the implementation of such relation into biogeochemical modelling, it should be considered that not only seasonal weather development but also phenological growth stages are determining the BVOC patterns and emission potentials.

Herbivore-induced BVOC emissions of Scots pine under warming, elevated ozone and increased nitrogen availability in an open-field exposure

Climate change may promote the frequency of insect attacks such as outbreaks of the great web-spinning pine sawfly (Acantholyda posticalis) on Scots pine (Pinus sylvestris L.). We determined the emission rates of localized biogenic volatile organic compounds (BVOCs) from A. posticalis-fed branches, and systemic BVOCs from non-fed branches of Scots pine seedlings defoliated for two growing seasons by A. posticalis larvae. Seedlings were also exposed to warming, elevated ozone and higher nitrogen availability for three years in an open-field experiment. A. posticalis feeding increased localized emissions of total non-oxygenated monoterpenes 21-fold, total oxygenated monoterpenes 9.1-fold, total sesquiterpenes 11-fold and total green leaf volatiles 9.2-fold from insect-damaged shoots on the 7th day of feeding in June. Warming reduced the effects of herbivory on the emission rates of total non-oxygenated monoterpenes by 77%. However, the effect of herbivory on total sesquiterpene emissions was enhanced by 16-fold in combination with warming and elevated ozone. The localized emission rates of total BVOCs were linearly increased when feeding damage intensity by larvae exceeded 80%. After three weeks of continuous sawfly feeding, herbivory stress increased systemic emissions of total non-oxygenated monoterpenes 5.6-fold, total sesquiterpenes 5.6-fold and total green leaf volatiles 6.5-fold from the non-damaged branch of larvae-fed seedlings, and this effect on total non-oxygenated monoterpene emission was enhanced 8.6-fold with elevated ozone. Herbivory sporadically showed post-feeding effects still by the end of 12th week from the initiation of feeding, increasing total non-oxygenated monoterpene emissions 4.4-fold at elevated nitrogen level. Our results suggest that Scots pine, at least in seedling stage, will be a stronger source of BVOC emissions in future due to expected increase of sawfly outbreaks with climate warming and by increased herbivory interactions with abiotic climate change factors.

A modeling study of secondary organic aerosol formation from sesquiterpenes using the STOCHEM global chemistry and transport model

AbstractSesquiterpenes are one of the precursors of secondary organic aerosol (SOA) which can be an important global sources of organic aerosol (OA). Updating the chemistry scheme in the global chemistry transport model by incorporating an oxidation mechanism for β‐caryophyllene (representing all sesquiterpenes), adding global sesquiterpene emissions of 29 Tg/yr, and revising global monoterpene emissions up to 162 Tg/yr [Guenther et al., 2012] led to an increase of SOA burden by 95% and SOA production rate by 106% relative to the base case described in Utembe et al. [2011]. Including the emissions of sesquiterpenes resulted in increase of SOA burden of 0.11 Tg and SOA production rate of 12.9 Tg/yr relative to the base case. The highest concentrations of sesquiterpene‐derived SOA (by up to 1.2 μg/m3) were found over central Africa and South America, the regions having high levels of biogenic emissions with significant biomass burning. In the updated model simulation, the multigeneration oxidation products from sesquiterpenes and monoterpenes transported above the boundary layer and condensed to the aerosol phase at higher altitude led to an increase of OA by up to 30% over the tropics and northern midlatitude to higher altitude. The model evaluation showed an underestimation of model OA mostly for the campaigns dominated by regional anthropogenic pollution. The increase of SOA production from sesquiterpenes reduced the discrepancies between modeled and observed OA concentrations over the remote and rural areas. The increase of SOA concentrations by up to 200% from preindustrial to present scenarios was found over the tropical oceans.

Terpenoid and carbonyl emissions from Norway spruce in Finland during the growing season

Abstract. We present spring and summer volatile organic compound (VOC) emission rate measurements from Norway spruce (Picea abies L. Karst) growing in a boreal forest in southern Finland. The measurements were conducted using in situ gas chromatograph with 1 to 2 h time resolution to reveal quantitative and qualitative short-term and seasonal variability of the emissions. The measurements cover altogether 14 weeks in years 2011, 2014 and 2015. Monoterpene (MT) and sesquiterpene (SQT) emission rates were measured all the time, but isoprene only in 2014 and 2015 and acetone and C4–C10 aldehydes only in 2015. The emission rates of all the compounds were low in spring, but MT, acetone, and C4–C10 aldehyde emission rates increased as summer proceeded, reaching maximum emission rates in July. Late summer mean values (late July and August) were 29, 17, and 33 ng g(dw)−1 h−1 for MTs, acetone, and aldehydes respectively. SQT emission rates increased during the summer and highest emissions were measured in late summer (late summer mean value 84 ng g(dw)−1 h−1) concomitant with highest linalool emissions most likely due to stress effects. The between-tree variability of emission pattern was studied by measuring seven different trees during the same afternoon using adsorbent tubes. Especially the contributions of limonene, terpinolene, and camphene were found to vary between trees, whereas proportions of α-pinene (25 ± 5 %) and β-pinene (7 ± 3 %) were more stable. Our results show that it is important to measure emissions at canopy level due to irregular emission pattern, but reliable SQT emission data can be measured only from enclosures. SQT emissions contributed more than 90 % of the ozone reactivity most of the time, and about 70 % of the OH reactivity during late summer. The contribution of aldehydes to OH reactivity was comparable to that of MT during late summer, 10–30 % most of the time.

New insights into the parametrization of temperature and light responses of mono - and sesquiterpene emissions from Aleppo pine and rosemary

Phytogenic emission of large volatile organic compounds (VOCs) such as monoterpenes (MTs) and sesquiterpenes (SQTs) are key precursors to the formation and growth of atmospheric particles. However, controlled environment studies to elucidate emission responses to temperature and light are still sparse. In this study, the volatile contents and emission responses of Aleppo pine and Rosemary have been investigated. These two common Mediterranean species store semivolatiles inside (resin ducts) and outside (trichomes) their foliage tissues respectively. Both species emitted mainly MTs with basal emission rates of around 5 (Rosemary) and 10 (pine) μg g−1 h−1 and SQTs about one order of magnitude lower. In Aleppo pine, two volatile sources could be clearly distinguished: 1) de-novo synthesized emission of (E)-β-ocimene and linalool, which accounted for about 70% of the total VOC release, were not found in foliar VOC extracts and expressed light dependency (LD) and temperature responses typical for enzyme driven emissions; and 2) storage-derived emissions of various MTs and SQTs whose emissions increased exponentially with temperature, showed no light dependency and were all present in leaf extracts. In Rosemary, all emitted MTs and SQTs including many oxygenated compounds, showed responses typical for stored volatiles and were all found in leaf extracts. The emissions of individual volatiles or volatile classes could be well described with the commonly applied empirical algorithms developed for LD or non LD emissions. However, the shapes of the temperature responses, and hence the deduced coefficient values, were significantly different between oxygenated and non-oxygenated compounds. They also differed between the storage-derived emissions of the two plant species, for individual VOCs or VOC classes. We address the possible reasons for this variation in temperature responses and argue that they are mostly due to molecular interactions along the species specific leaf-internal diffusion paths including the build-up of transient VOC pools and degradation.