Monoterpene Emissions Research Articles

Phenological stage of tundra vegetation controls bidirectional exchange of BVOCs in a climate change experiment on a subarctic heath.

Traditionally, biogenic volatile organic compound (BVOC) emissions are often considered a unidirectional flux, from the ecosystem to the atmosphere, but recent studies clearly show the potential for bidirectional exchange. Here we aimed to investigate how warming and leaf litter addition affect the bidirectional exchange (flux) of BVOCs in a long‐term field experiment in the Subarctic. We also assessed changes in net BVOC fluxes in relation to the time of day and the influence of different plant phenological stages. The study was conducted in a full factorial experiment with open top chamber warming and annual litter addition treatments in a tundra heath in Abisko, Northern Sweden. After 18 years of treatments, ecosystem‐level net BVOC fluxes were measured in the experimental plots using proton‐transfer‐reaction time‐of‐flight mass spectrometry (PTR–ToF–MS). The warming treatment increased monoterpene and isoprene emissions by ≈50%. Increasing temperature, due to diurnal variations, can both increase BVOC emission and simultaneously, increase ecosystem uptake. For any given treatment, monoterpene, isoprene, and acetone emissions also increased with increasing ambient air temperatures caused by diurnal variability. Acetaldehyde, methanol, and sesquiterpenes decreased likely due to a deposition flux. For litter addition, only a significant indirect effect on isoprene and monoterpene fluxes (decrease by ~50%–75%) was observed. Litter addition may change soil moisture conditions, leading to changes in plant species composition and biomass, which could subsequently result in changes to BVOC emission compositions. Phenological stages significantly affected fluxes of methanol, isoprene and monoterpenes. We suggest that plant phenological stages differ in impacts on BVOC net emissions, but ambient air temperature and photosynthetically active radiation (PAR) also interact and influence BVOC net emissions differently. Our results may also suggest that BVOC fluxes are not only a response to changes in temperature and light intensity, as the circadian clock also affects emission rates.

Diurnal variation in BVOC emission and CO2 gas exchange from above- and belowground parts of two coniferous species and their responses to elevated O3.

Increased tropospheric ozone (O3) concentrations in boreal forests affect the emission of biogenic volatile organic compounds (BVOCs), which play crucial roles in biosphere-atmosphere feedbacks. Although it has been well documented that BVOC emissions are altered in response to elevated O3, consequent effects on the carbon budget have been largely unexplored. Here, we studied the effects of elevated O3 (80nmolmol-1) on diurnal variation of BVOC emissions and gas exchange of CO2 from above- and belowground parts of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) and further investigated effects on the carbon budget. In spring, elevated O3 decreased BVOC emissions and net photosynthesis rate (Pn) from above-ground parts of both species. As BVOC emissions have a causal relationship with dormancy recovery, O3-induced decreases in BVOC emissions indicated the inhibition of dormancy recovery. Contrary to the spring results, in summer BVOC emissions from aboveground parts were increased in response to elevated O3 in both species. Decreases in Pn indicated O3 stress. O3-induced monoterpene emissions from aboveground were the main volatile defense response. Elevated O3 had little effect on BVOC emissions from belowground parts of either species in spring or summer. In spring, elevated O3 decreased the proportion of carbon emitted as BVOCs relative to that assimilated by photosynthesis (the proportion of BVOC-C loss) at the soil-plant system levels in both species. In summer, elevated O3 resulted in a net CO2-C loss at the soil-plant system level of Scots pine. During this process, O3-induced BVOC-C loss can represent a significant fraction of carbon exchange between the atmosphere and Scots pine. In Norway spruce, the effects of O3 were less pronounced. The current results highlight the need for prediction of BVOC emissions and their contributions to the carbon budget in boreal forests under O3 stress.

Toxicological Responses of α-Pinene-Derived Secondary Organic Aerosol and Its Molecular Tracers in Human Lung Cell Lines.

Secondary organic aerosol (SOA) is a major component of airborne fine particulate matter (PM2.5) that contributes to adverse human health effects upon inhalation. Atmospheric ozonolysis of α-pinene, an abundantly emitted monoterpene from terrestrial vegetation, leads to significant global SOA formation; however, its impact on pulmonary pathophysiology remains uncertain. In this study, we quantified an increasing concentration response of three well-established α-pinene SOA tracers (pinic, pinonic, and 3-methyl-1,2,3-butanetricarboxylic acids) and a full mixture of α-pinene SOA in A549 (alveolar epithelial carcinoma) and BEAS-2B (bronchial epithelial normal) lung cell lines. The three aforementioned tracers contributed ∼57% of the α-pinene SOA mass under our experimental conditions. Cellular proliferation, cell viability, and oxidative stress were assessed as toxicological end points. The three α-pinene SOA molecular tracers had insignificant responses in both cell types when compared with the α-pinene SOA (up to 200 μg mL–1). BEAS-2B cells exposed to 200 μg mL–1 of α-pinene SOA decreased cellular proliferation to ∼70% and 44% at 24- and 48-h post exposure, respectively; no changes in A549 cells were observed. The inhibitory concentration-50 (IC50) in BEAS-2B cells was found to be 912 and 230 μg mL–1 at 24 and 48 h, respectively. An approximate 4-fold increase in cellular oxidative stress was observed in BEAS-2B cells when compared with untreated cells, suggesting that reactive oxygen species (ROS) buildup resulted in the downstream cytotoxicity following 24 h of exposure to α-pinene SOA. Organic hydroperoxides that were identified in the α-pinene SOA samples likely contributed to the ROS and cytotoxicity. This study identifies the potential components of α-pinene SOA that likely modulate the oxidative stress response within lung cells and highlights the need to carry out chronic exposure studies on α-pinene SOA to elucidate its long-term inhalation exposure effects.

An uncertainty framework for i-Tree eco: A comparative study of 15 cities across the United States

Uncertainty information associated with urban forest models are beneficial for model transparency, model development, effective communication of model output, and decision-making. However, compared with the extensive studies based on the applications of urban forest models, little attention has been paid to the uncertainty of the output from these models. In this study, bootstrap and Monte Carlo simulation were employed to explore the uncertainty of i-Tree Eco. We assess the uncertainties associated with input data, sampling methods and models throughout the processes of urban forest structure and function quantification, and we propagate and aggregate the three sources of uncertainty to derive an estimator of total uncertainty. The uncertainty magnitude is expressed as the coefficient of variation. By applying the uncertainty framework to a network of 15 cities across the United States, we find that the average magnitude of total uncertainty across 15 cities is 12.3 % for leaf area, 13.4 % for carbon storage, 11.1 % for carbon sequestration, 40.7 % for isoprene emissions, and 25.0 % for monoterpene emissions. For leaf and carbon estimators, the total uncertainty is primarily driven by sampling uncertainty; the magnitudes of all three sources of uncertainty are comparable across 15 cities. In contrast, input, sampling, and model uncertainties all contribute to the total uncertainty for isoprene and monoterpene emission estimators, and there are large variations in these three sources of uncertainty across the 15 cities. An analysis of a regression-based approach to estimate input and model error indicated only moderate improvements over using averages across sites when estimating total uncertainty.

Monoterpenes from tropical forest and oil palm plantation floor in Malaysian Borneo/Sabah: emission and composition.

Regional estimates of VOC fluxes focus largely on emissions from the canopy and omit potential contributions from the forest floor including soil, litter and understorey vegetation. Here, we measured monoterpene emissions every 2 months over 2 years from logged tropical forest and oil palm plantation floor in Malaysian Borneo using static flux chambers. The main emitted monoterpenes were α-pinene, β-pinene and d-limonene. The amount of litter present was the strongest indicator for higher monoterpene fluxes. Mean α-pinene fluxes were around 2.5-3.5 μg C m-2 h-1 from the forest floor with occasional fluxes exceeding 100 μg C m-2 h-1. Fluxes from the oil palm plantation, where hardly any litter was present, were lower (on average 0.5-2.9 μg C m-2 h-1) and only higher when litter was present. All other measured monoterpenes were emitted at lower rates. No seasonal trends could be identified for all monoterpenes and mean fluxes from both forest and plantation floor were ~ 100 times smaller than canopy emission rates reported in the literature. Occasional spikes of higher emissions from the forest floor, however, warrant further investigation in terms of underlying processes and their contribution to regional scale atmospheric fluxes.

Seasonal and elevational variability in the induction of specialized compounds from mountain birch (Betula pubescens var. pumila) by winter moth larvae (Operophtera brumata).

The mountain birch [Betula pubescens var. pumila (L.)] forest in the Subarctic is periodically exposed to insect outbreaks, which are expected to intensify due to climate change. To mitigate abiotic and biotic stresses, plants have evolved chemical defenses, including volatile organic compounds (VOCs) and non-volatile specialized compounds (NVSCs). Constitutive and induced production of these compounds, however, are poorly studied in Subarctic populations of mountain birch. Here, we assessed the joint effects of insect herbivory, elevation and season on foliar VOC emissions and NVSC contents of mountain birch. The VOCs were sampled in situ by an enclosure technique and analyzed by gas chromatography–mass spectrometry. NVSCs were analyzed by liquid chromatography–mass spectrometry using an untargeted approach. At low elevation, experimental herbivory by winter moth larvae (Operophtera brumata) increased emissions of monoterpenes and homoterpenes over the 3-week feeding period, and sesquiterpenes and green leaf volatiles at the end of the feeding period. At high elevation, however, herbivory augmented only homoterpene emissions. The more pronounced herbivory effects at low elevation were likely due to higher herbivory intensity. Of the individual compounds, linalool, ocimene, 4,8-dimethylnona-1,3,7-triene, 2-methyl butanenitrile and benzyl nitrile were among the most responsive compounds in herbivory treatments. Herbivory also altered foliar NVSC profiles at both low and high elevations, with the most responsive compounds likely belonging to fatty acyl glycosides and terpene glycosides. Additionally, VOC emissions from non-infested branches were higher at high than low elevation, particularly during the early season, which was mainly driven by phenological differences. The VOC emissions varied substantially over the season, largely reflecting the seasonal variations in temperature and light levels. Our results suggest that if insect herbivory pressure continues to rise in the mountain birch forest with ongoing climate change, it will significantly increase VOC emissions with important consequences for local trophic interactions and climate.

Seasonal emission of monoterpenes from four chemotypes of Cinnamomum camphora

Plant terpenes are the main functional agents in forest bathing and have great value in several industries. To uncover the seasonal variation of Cinnamomum camphora monoterpene emission and the difference among the chemotypes for promoting the development of forest bathing and exploitation of monoterpenes using the species, the emission of monoterpenes and related gene expression in the camphor chemotype, eucalyptol chemotype, linalool chemotype and borneol chemotype of C. camphora were analyzed in May (spring), July (summer) and November (autumn), and the stored monoterpenes and storage structure were investigated. Eleocytes were the storage structure of monoterpenes in C. camphora, which widely existed in the leaf palisade tissue and spongy tissue, as well as around the glands and vascular bundles. The 4 chemotypes of C. camphora released different monoterpene components which mainly derived from the immediate emission after synthesis. Camphor, eucalyptol, linalool and endo-borneol showed the uppermost emission rate and were the typical monoterpenes in the corresponding chemotype, respectively, due to the high expression of the genes encoding bornyl diphosphate synthase (E5.5.1.8), linalool synthase (TSP14) and (+)-neomenthol dehydrogenase (E1.1.1.208) for the biosynthesis of camphor, linalool and endo-borneol, respectively, and only expression of the gene encoding 1,8-cineole synthase (TSP-cin) for eucalyptol biosynthesis. Among the 4 chemotypes, the linalool chemotype showed the highest emission rate of monoterpenes in the same month (without significant difference with the eucalyptol chemotype in November), due to the high expression of the genes (dxs, dxr, ispF, gcpE, and GGPS) in methylerythritol-4-phosphate (MEP) pathway, α-terpineol synthase gene (E4.2.3.111) and TSP14. Among the 3 months, temperature was the remarkably varied meteorological condition. The highest monoterpene emission rate from the 4 chemotypes of C. camphora was detected in July, which should result from the up-regulated expression of related genes in monoterpene biosynthesis and improved vaporization and diffusion of stored monoterpenes under high temperature, with the former providing a major contribution.

Leaf Monoterpene Emission Limits Photosynthetic Downregulation under Heat Stress in Field-Grown Grapevine.

Rising temperature is among the most remarkably stressful phenomena induced by global climate changes with negative impacts on crop productivity and quality. It has been previously shown that volatiles belonging to the isoprenoid family can confer protection against abiotic stresses. In this work, two Vitis vinifera cv. ‘Chardonnay’ clones (SMA130 and INRA809) differing due to a mutation (S272P) of the DXS gene encoding for 1-deoxy-D-xylulose-5-phosphate (the first dedicated enzyme of the 2C-methyl-D-erythritol-4-phosphate (MEP) pathway) and involved in the regulation of isoprenoids biosynthesis were investigated in field trials and laboratory experiments. Leaf monoterpene emission, chlorophyll fluorescence and gas-exchange measurements were assessed over three seasons at different phenological stages and either carried out in in vivo or controlled conditions under contrasting temperatures. A significant (p < 0.001) increase in leaf monoterpene emission was observed in INRA809 when plants were experiencing high temperatures and over two experiments, while no differences were recorded for SMA130. Significant variation was observed for the rate of leaf CO2 assimilation under heat stress, with INRA809 maintaining higher photosynthetic rates and stomatal conductance values than SMA130 (p = 0.003) when leaf temperature increased above 30 °C. At the same time, the maximum photochemical quantum yield of PSII (Fv/Fm) was affected by heat stress in the non-emitting clone (SMA130), while the INRA809 showed a significant resilience of PSII under elevated temperature conditions. Consistent data were recorded between field seasons and temperature treatments in controlled environment conditions, suggesting a strong influence of monoterpene emission on heat tolerance under high temperatures. This work provides further insights on the photoprotective role of isoprenoids in heat-stressed Vitis vinifera, and additional studies should focus on unraveling the mechanisms underlying heat tolerance on the monoterpene-emitter grapevine clone.

Seasonal variation of monoterpene emissions from forest floor and its contribution to whole canopy flux in a &lt;i&gt;Larix kaempferi&lt;/i&gt; forest

Seasonal variation of monoterpene emissions from forest floor and its contribution to whole canopy flux in a &lt;i&gt;Larix kaempferi&lt;/i&gt; forest

Assessing Regional Model Predictions of Wintertime SOA from Aromatic Compounds and Monoterpenes with Precursor-specific Tracers

ABSTRACT The Community Multiscale Air Quality (CMAQ) model, with modifications to track precursor-specific SOA, was applied to model SOA formation from aromatic compounds and monoterpenes in Shanghai in November 2018. The modeled total aromatic SOA showed a strong correlation with measured 2,3-dihydroxy-4-oxopentanoic acid (DHOPA) concentrations in the ambient aerosols (R > 0.5 for hourly data and R > 0.75 for daily average data). The ratios of observed DHOPA and modeled aromatic SOA with all components included is around (0.5–1.6) × 10–3, lower than the commonly used ratio of 4 × 10–3 determined for toluene in a series of smog chamber experiments. This suggests that aromatic SOA could be underestimated when directly using the chamber-derived ratios. The predicted monoterpene SOA shows a stronger correlation with the sum of two α-pinene tracers (α-pinT), pinic acid and 3-MBTCA, with R > 0.6 and R > 0.8 for hourly and daily data, respectively. The α-pinT to modeled monoterpene SOA ratios are 0.13–0.25, which generally match the ratio of 0.168 ± 0.081 reported in chamber studies. However, since the current model does not treat α-pinene and its SOA explicitly, future modeling studies should include a more detailed treatment of monoterpene emissions and reactions to predict SOA from these important precursors and compare with the ambient precursor-specific SOA-tracers.

Gall- and erineum-forming Eriophyes mites alter photosynthesis and volatile emissions in an infection severity-dependent manner in broad-leaved trees Alnus glutinosa and Tilia cordata.

Highly host-specific eriophyoid gall- and erineum-forming mites infest a limited range of broadleaf species, with the mites from the genus Eriophyes particularly widespread on Alnus spp. and Tilia spp. Once infected, the infections can be massive, covering a large part of leaf area and spreading through the plant canopy, but the effects of Eriophyes mite gall formation on the performance of host leaves are poorly understood. We studied the influence of three frequent Eriophyes infections, E. inangulis gall-forming mites on Alnus glutinosa, and E. tiliae gall-forming and E. exilis erineum-forming mites on Tilia cordata, on foliage morphology, chemistry, photosynthetic characteristics, and constitutive and induced volatile emissions. For all types of infections, leaf dry mass per unit area, net assimilation rate per area and stomatal conductance strongly decreased with increasing severity of infection. Mite infections resulted in enhancement or elicitation of emissions of fatty acid-derived volatiles, isoprene, benzenoids and carotenoid breakdown products in an infection severity-dependent manner for all different infections. Monoterpene emissions were strongly elicited in T. cordata mite infections, but these emissions were suppressed in E. inangulis-infected A. glutinosa. Although the overall level of mite-induced emissions was surprisingly low, these results highlight the uniqueness of the volatile profiles and offer opportunities for using volatile fingerprints and overall emission rates to diagnose infections by Eriophyes gall- and erineum-forming mites on temperate trees and assess their impact on the physiology of the affected trees.

Emissions of gaseous formic and acetic acids from major tree species in Japan

Gaseous formic and acetic acids are directly emitted from vegetation and produced by the photooxidation of biogenic volatile organic compounds in the atmosphere. Gaseous formic and acetic acid emissions from trees have not been well studied in Japan and the Asian region, and to gain further knowledge in this respect, we measured the emissions of formic and acetic acid emissions together with isoprene and monoterpene emissions from 10 major forest tree species and 10 major road tree species. All of the measured trees were found to emit gaseous formic and acetic acids from their leaves, but not all species emitted isoprene or monoterpene. The emission rates of formic (0.05–1.3 μg gDW−1 h−1) and acetic (0.10–1.43 μg gDW−1 h−1) acids were similar to those of some trees in Europe but higher than those of tropical tree species. No monthly variations were found in the emission rates of formic and acetic acids, but the emission rates of isoprene and monoterpene showed clear monthly variations. We calculated the ratio of direct emissions to direct plus secondary production derived by the photooxidation of formic and acetic acids by isoprene and monoterpene (direct/total emission ratio) relating to major forest and road tree species in Japan. For isoprene and monoterpene emitters, the average values of the direct/total emission ratio of formic and acetic acids in August were 62% (range: 9.0–88%) and 64% (range: 6.2–90%), respectively. The contribution degree of the direct/total emission ratio differed depending on the isoprene and monoterpene emission rates. The findings are suggestive of the importance of both direct emissions of gaseous formic and acetic acids from trees and the secondary formation of these acids via isoprene and monoterpene photooxidation. The present study may be useful for improving the estimation accuracy of formic and acetic acid emissions from vegetation in future climate change and air quality studies.

Effects of elevated CO2 on photosynthetic characteristics and monoterpene emissions in Pinus massoniana seedlings

Effects of elevated CO2 on photosynthetic characteristics and monoterpene emissions in Pinus massoniana seedlings

The importance of accounting for enhanced emissions of monoterpenes from new Scots pine foliage in models - A Finnish case study

Models to predict the emissions of biogenic volatile organic compounds (BVOCs) from terrestrial vegetation largely use standardised emission potentials derived from shoot enclosure measurements of mature foliage. In these models, the potential of new foliage to emit BVOCs is assumed to be similar, or up to twice as high, as that of mature foliage, and thus new conifers foliage is predicted to have a negligible to minor contribution to canopy BVOC emissions during spring time due to the small foliage mass of emerging and growing needles. Extensive observations have, however, recently demonstrated that the potential of new Scots pine needles to emit several different BVOCs can be up to about 500 times higher than that of the corresponding mature foliage. Thus, we build on these discoveries and investigate the potential impact of considering these enhanced emissions from new Scots pine foliage on estimates of monoterpene emissions and new atmospheric aerosol particle formation and their subsequent growth. We show that the importance of taking the enhanced monoterpene emission potential of new Scots pine foliage into account decreases as a function of season, tree age and latitude, and that new foliage could be responsible for the majority of the whole tree's foliage emissions of monoterpenes during spring time, independently of tree age and location. Our results suggest that annual monoterpene emission estimates from Finland would increase with up to ~25% if the enhanced emissions from new Scots pine foliage were also considered, with the majority being emitted during spring time where also new particle formation has been observed to occur most frequently. We estimate that our findings can lead to increases in predictions of the formation rates of 2 nm particles during spring time by ~75–280% in northern Finland and by ~130–870% in southern Finland. Likewise, simulated growth rates of 2–3 nm particles would increase by ~65–180% in northern Finland and by ~110–520% in southern Finland if the enhanced emissions of monoterpenes from new Scots pine foliage were explicitly considered. Since only one measurement study (Aalto et al., 2014), on which our work builds, has so far found highly pronounced emissions of monoterpenes from new Scots pine foliage compared to those of mature, we conclude that more spring time measurements of new conifers foliage are required for improving emission algorithms in biogenic emission models. • In models, emission potentials of new and mature foliage are assumed to be similar. • VOCs emissions from new vs mature pine foliage can differ by 2–3 orders of magnitude. • Accounting for new foliage emissions significantly impacts annual emission estimates. • Enhanced springtime emissions can lead to enhanced aerosol formation and growth.

Nitrogen addition inhibits total monoterpene emissions in subtropical forest floor of South China

Monoterpenes (MTs) play crucial roles not only in atmospheric chemistry and global climate change but also in soil processes and soil ecology. Elevated nitrogen (N) deposition can influence soil microbial community and litter decomposition, and consequently alters MT fluxes from forest floors and litter. Yet, the responses of soil and litter MT to increased N deposition remain poorly understood and the influences of N addition are sometimes contradictory. In the present study, static chambers were placed in masson pine forest (PF) and in monsoon evergreen broad-leaf forest (BF) at Dinghushan, subtropical China. The preconcentrator-GC-MS was used to analyze the effect of N addition on MT fluxes from the forest floors and litter. The results showed that under control treatment (without N addition), the total MT emission rates were 279.90±137.17 and 102.70±45.36 pmol m−2 s−1 in the PF and BF floors, respectively, with a-pinene being the largest MT species in the PF and limonene in the BF. α-pinene and β-pinene emission rates decreased significantly in both forest floors after N addition, whereas a diverse trend was found for limonene and camphene in the PF floor. Furthermore, some MT fluxes showed significant negative correlations with soil respiration and soil temperature. Litter was important in MT fluxes from forest floors and its emission rates were enhanced by N addition. Moreover, different MT response to elevated N was found between the forest floor and litter. This study indicated that the elevated N deposition in the future would inhibit the MT emissions from the subtropical forest floor.

Measurements of total ozone reactivity in a suburban forest in Japan

To investigate tropospheric ozone, O3, and secondary organic aerosols, SOAs, reactivities of biogenic volatile organic compounds, BVOCs, with atmospheric oxidants have been focused on. In this study, as an ensemble monitor covering all ozone-reactive BVOCs, the analyzer of total ozone reactivity, RO3, was modified and applied to the ambient observation of RO3 in a forest. The analyzer was improved to realize the RO3 measurements of ambient BVOCs in low concentration. After improvement, the typical limit of detection of present RO3 analyzer was determined as 1.5 × 10−5 s−1 (S/N = 3, 600-s average) under laboratory conditions. For the atmospheric observation, it is important to consider coexisting compounds in the ambient air. It was confirmed that the configurations of dual chemiluminescence detectors (CLDs) could reasonably cancel out the contributions of ambient ozone. It is also necessary to distinguish the contributions of NO (RNO) from total ozone reactivity (RALL). The method for quantifying RNO was also established. Contributions of VOCs, RO3, to RALL were acquired by subtracting those of NO and NO2 from measured RALL. It was confirmed that the present analyzer had capability to quantify RO3 down to 4 × 10−5 s−1 as the overall limit of detection under ambient conditions. Then, trial observations of RO3 were conducted in a suburban forest in Japan. RO3 data were acquired successfully for a total of 8 days, including high temperature days over 35 °C. It was confirmed that RO3 could be significantly quantified utilizing the present analyzer when temperature was high enough and NO level was insignificantly low. Fractional contributions of VOC, NO, and NO2 to O3 loss reactions were also investigated. As a result of regression analysis between RO3 and temperature, a clear dependence of RO3 on temperature was observed in the afternoon. When the temperature dependent algorithm was considered, the temperature sensitivity was acquired as 0.23 ± 0.03 K−1 (26% K−1), which was comparable to those in previous studies on monoterpene emission from vegetation. The RO3 analyzer might also capture the early morning peak of monoterpene emission in a forest though the uncertainties were large due to fluctuations of NO. Consequently, it was confirmed that the present RO3 analyzer be useful for investigating BVOCs in a forest. Especially, monoterpene emission under elevated temperature conditions up to 36.2 °C was significantly captured during the RO3 observation in the forestal atmosphere.

Expected Impacts of Mixing European Beech with Silver Fir on Regional Air Quality and Radiation Balance

The anticipated climate change during the next decades is posing crucial challenges to ecosystems. In order to decrease the vulnerability of forests, introducing tree species’ mixtures are a viable strategy, with deep-rooting native Silver fir (Abies alba) being a primary candidate for admixture into current pure stands of European beech (Fagus sylvatica) especially in mountainous areas. Such a change in forest structure also has effects on the regional scale, which, however, have been seldomly quantified. Therefore, we measured and modeled radiative balance and air chemistry impacts of admixing Silver fir to European beech stands, including changes in biogenic volatile organic compound emissions. An increased fraction of Silver fir caused a smaller albedo and a (simulated) larger evapotranspiration, leading to a dryer and warmer forest. While isoprene emission was negligible for both species, sesquiterpene and monoterpene emissions were larger for fir than for beech. From these differences, we derived that ozone concentration as well as secondary organic aerosols and cloud condensation nuclei would increase regionally. Overall, we demonstrated that even a relatively mild scenario of tree species change will alter the energy balance and air quality in a way that could potentially influence the climate on a landscape scale.

Electrophysiological Responses of the Beech Leaf-Mining Weevil, Orchestes fagi, to Seasonally-Variant Volatile Organic Compounds Emitted by American Beech, Fagus grandifolia.

The beech leaf-mining weevil, Orchestes fagi, is a common pest of European beech, Fagus sylvatica, and has recently become established in Nova Scotia, Canada where it similarly infests American beech, F. grandifolia. We collected volatile organic compounds (VOCs) emitted by F. grandifolia leaves at five developmental stages over one growing season and simultaneously analyzed them for volatile emissions and O. fagi antennal response using gas chromatography-electroantennographic detection (GC-EAD). Volatile profiles changed significantly throughout the growing season, shifting from primarily β-caryophyllene, methyl jasmonate, and simple monoterpene emissions to dominance of the bicyclic monoterpene sabinene during maturity. Two VOCs dominant during bud burst, (R)-(+)-limonene and geranyl-p-cymene, may be of biological relevance due to the highly specific oviposition period of O. fagi at this stage though antennal responses were inconclusive. Senescence showed a decrease in blend complexity with an increase in (Z)-3-hexenyl acetate and (Z)-3-hexen-1-ol as well as a resurgence of α-terpinene and geranyl-p-cymene. We present a novel electroantennal preparation for O. fagi. Antennae of both male and female O. fagi responded to the majority of detectable peaks for host volatiles presented via GC-EAD. Females displayed greater overall sensitivities and less specificity to host volatiles and it is hypothesized that this translates to more generalist olfaction than males. It is clear that olfactory cues are important physiologically though their implications on behaviour are still unknown. The results presented in this study provide a baseline and tools on which to connect the complex and highly time-specific phenology of both F. grandifolia and the destructive pest O. fagi through which olfactory-based lures can be investigated for monitoring systems.

Pituranthos tortuosus Essential Oil from Libya: Season Effect on the Composition and Antioxidant Activity

Pituranthos tortuosus has multi-local traditional applications, production of aroma, in culinary processes, killing insects and as a remedy for diabetes, infectious diseases, dyspepsia, inflammation, fever and hepatitis. The essential oil antioxidant quality and composition of the dried aerial part of P. tortuosus collected at two successive seasons (spring and summer) were investigated. Essential oils were obtained by hydrodistilla- tion, physically evaluated and analyzed by the GC-MS. The ability of the oil-batches to restore the glutathione level in the alloxan-induced diabetic rats was used to assess the antioxidant quality. A total of twenty-eight com- pounds representing 98.65 % of the 0.8 % oil-yields and nineteen compounds representing 98.39 % of the 0.3 % oil-yields were identified in the summer and spring oil-batches, respectively. The oxygenated (38.47 %) and non-oxygenated (36.31 %) monoterpenes were accumulated in the spring oil-batch. In contrast, sesquiterpenes were accumulated in the summer oil-batch which may reflects the effect of monoterpenes emission due to summer temperature and the different biosynthetic preferability of the plant during summer and spring seasons. 1,8-cineole (13.43 %), 9-epi-caryophyllene (11.62 %) and α-cadinol (21.51 %) were the major constituents of summer oil-batch, while α-thujene (21.22 %) and linalool (27.98 %) were major components of spring oil- batch. The glutathione level was restored significantly (P< 0.05) in the animal treated with summer (33.6 %) and spring (32.8 %) oil-batches compared to the alloxan diabetic animals (21.3 %). In conclusion, major chemical changes were recognized in the summer and spring volatile oil-batches evidenced by the variations in the percentages of the monoterpenes and sesquiterpenes in these oil-batches which affect the antioxidant quality of the oils.

Enhanced monoterpene emission in transgenic orange mint (Mentha × piperita f. citrata) overexpressing a tobacco lipid transfer protein (NtLTP1).

Overexpression of the tobacco lipid transfer protein (NtLTP1) gene in transgenic orange mint resulted in enhanced accumulation of monoterpenes in the cavity of head cells of glandular trichomes, which resulted in enhanced emission of monoterpenes from transgenic orange mints. Plants in the genus Mentha (Lamiaceae) produce volatile oils that accumulate in peltate glandular trichomes in the aerial parts of plants. A lipid transfer protein (NtLTP1) in tobacco showed glandular trichome-specific expression and supported the secretion of diterpenoid lipids from head cells of glandular trichomes (Choi et al., Plant J 70:480-491,2012). Here, we constructed transgenic orange mint (Mentha × piperita f. citrata) overexpressing the tobacco NtLTP1 gene via Agrobacterium-mediated transformation. Transgenic lines of orange mint overexpressing NtLTP1 were confirmed by genomic PCR and RT-PCR. Immunoblotting analysis using an NtLTP1 polyclonal antibody showed clear dark spots at the position of the lipid exudates from tobacco glandular trichomes and the squeezed out lipids from the glandular trichomes of transgenic orange mint. Heads of glandular trichomes in transgenic plants overexpressing the NtLTP1 gene showed a larger diameter than those of the wild-type control. The enhanced size of trichome heads in transgenic orange mint was confirmed by scanning electron microscopy. Volatile components were extracted from wild-type and transgenic orange mint by solid-phase microextraction (SPME) and analyzed by headspace-gas chromatography-mass spectrometry (HS/GC/MS). Linalyl acetate was the most abundant component among the eleven identified monoterpenes in the volatile compounds extracted from both the wild-type and transgenic lines of orange mint. Overexpression of NtLTP1 in transgenic orange mint plants resulted in enhanced emission of volatile monoterpenoids compared with that of volatile monoterpenoids in the wild-type control plants.