Emission of monoterpenes from European beech (<i>Fagus</i><i> sylvatica</i> L.) as a function of light and temperature

International audienceUsing a dynamic branch enclosure technique European beech (Fagus sylvatica L.) was characterised as a strong emitter of monoterpenes, with sabinene being the predominant compound released. Since monoterpene emission was demonstrated to be a function of light and temperature, application of light and temperature dependent algorithms resulted in reasonable agreement with the measured data. Furthermore, during high temperature periods the depression of net CO2 exchange during midday (midday depression) was accompanied by a depression of monoterpene emission on one occasion. The species dependent standard emission factor and the light and temperature regulated release of monoterpenes is of crucial importance for European VOC emissions. All measurements were performed within the framework of the ECHO project (Emission and CHemical transformation of biogenic volatile Organic compounds) during two intensive field campaigns in the summers of 2002 and 2003

Significant light and temperature dependent monoterpene emissions from European beech (fagus sylvatiga L.) and their potential impact on the European VOC budget

By using a dynamic branch enclosure system the emission of monoterpenes from European beech (Fagus sylvatica L.) was investigated during two consecutive summer vegetation periods in the years of 2002 and 2003 in Germany. All measurements were performed under field conditions within the framework of the ECHO project (Emission and Chemical Transformation of Biogenic Volatile Organic Compounds, AFO 2000). European beech was characterized as a substantial emitter of monoterpenes, with sabinene being the predominant compound released. The monoterpene emission from European beech was shown to be a function of light and temperature and agreed well to emission algorithms that consider a light and temperature dependent release of volatile organics. Standard emission factors that were measured from these sunlit leaves of European beech ranged up to 4–13 µg g-1 h-1 (normalized to 1000 µmol m-2 s-1, 30°C) in the years of 2003 and 2002, respectively. The nighttime emission of monoterpene compounds was negligible. Also the artificial darkening of the sunlit branch during daylight conditions led to an immediate cessation of monoterpene emission. European beech is the dominating deciduous tree species in Europe. To demonstrate the effect of an updated monoterpene emission factor for European beech in combination with the consideration of a light and temperature dependent monoterpene emission, we applied a species based model simulation on a European scale. With respect to conventional estimates of the European volatile organic compound budget, the latter simulation resulted in relative increases of 16% by taking solely this tree species into account. On local scales these increases exceeded even more than 100% depending on the respective vegetation area coverage of European beec

Isoprene and monoterpene fluxes from central amazonian rainforest inferred from tower-based and airborne measurements, and implications on the atmospheric chemistry and the local carbon budget

We estimated the isoprene and monoterpene source strengths of a pristine tropical forest north of Manaus in the central Amazon Basin using three different micrometeorological flux measurement approaches. During the early dry season campaign of the Cooperative LBA Airborne Regional Experiment (LBA-CLAIRE-2001), a tower-based surface layer gradient (SLG) technique was applied simultaneously with a relaxed eddy accumulation (REA) system. Airborne measurements of vertical profiles within and above the convective boundary layer (CBL) were used to estimate fluxes on a landscape scale by application of the mixed layer gradient (MLG) technique. The mean daytime fluxes of organic carbon measured by REA were 2.1 mg C m^−2 h^−1 for isoprene, 0.20 mg C m^−2 h^−1 for α-pinene, and 0.39 mg C m^−2 h^−1 for the sum of monoterpenes. These values are in reasonable agreement with fluxes determined with the SLG approach, which exhibited a higher scatter, as expected for the complex terrain investigated. The observed VOC fluxes are in good agreement with simulations using a single-column chemistry and climate model (SCM).\ud \ud In contrast, the model-derived mixing ratios of VOCs were by far higher than observed, indicating that chemical processes may not be adequately represented in the model. The observed vertical gradients of isoprene and its primary degradation products methyl vinyl ketone (MVK) and methacrolein (MACR) suggest that the oxidation capacity in the tropical CBL is much higher than previously assumed. A simple chemical kinetics model was used to infer OH radical concentrations from the vertical gradients of (MVK+MACR)/isoprene. The estimated range of OH concentrations during the daytime was 3–8×10^6 molecules cm^−3, i.e., an order of magnitude higher than is estimated for the tropical CBL by current state-of-the-art atmospheric chemistry and transport models. The remarkably high OH concentrations were also supported by results of a simple budget analysis, based on the flux-to-lifetime relationship of isoprene within the CBL. Furthermore, VOC fluxes determined with the airborne MLG approach were only in reasonable agreement with those of the tower-based REA and SLG approaches after correction for chemical decay by OH radicals, applying a best estimate OH concentration of 5.5×10^6 molecules cm^−3. The SCM model calculations support relatively high OH concentration estimates after specifically being constrained by the mixing ratios of chemical constituents observed during the campaign.\ud \ud The relevance of the VOC fluxes for the local carbon budget of the tropical rainforest site during the measurements campaign was assessed by comparison with the concurrent CO2 fluxes, estimated by three different methods (eddy correlation, Lagrangian dispersion, and mass budget approach). Depending on the CO2 flux estimate, 1–6% or more of the carbon gained by net ecosystem productivity appeared to be re-emitted through VOC emissions

Tspan8 is expressed in breast cancer and regulates E-cadherin/catenin signalling and metastasis accompanied by increased circulating extracellular vesicles

Tspan8 exhibits a functional role in many cancer types including pancreatic, colorectal, oesophagus carcinoma, and melanoma. We present a first study on the expression and function of Tspan8 in breast cancer. Tspan8 protein was present in the majority of human primary breast cancer lesions and metastases in the brain, bone, lung, and liver. In a syngeneic rat breast cancer model, Tspan8$^{+}$ tumours formed multiple liver and spleen metastases, while Tspan8$^{-}$ tumours exhibited a significantly diminished ability to metastasise, indicating a role of Tspan8 in metastases. Addressing the underlying molecular mechanisms, we discovered that Tspan8 can mediate up‐regulation of E‐cadherin and down‐regulation of Twist, p120‐catenin, and β‐catenin target genes accompanied by the change of cell phenotype, resembling the mesenchymal–epithelial transition. Furthermore, Tspan8$^{+}$ cells exhibited enhanced cell–cell adhesion, diminished motility, and decreased sensitivity to irradiation. As a regulator of the content and function of extracellular vesicles (EVs), Tspan8 mediated a several‐fold increase in EV number in cell culture and the circulation of tumour‐bearing animals. We observed increased protein levels of E‐cadherin and p120‐catenin in these EVs; furthermore, Tspan8 and p120‐catenin were co‐immunoprecipitated, indicating that they may interact with each other. Altogether, our findings show the presence of Tspan8 in breast cancer primary lesion and metastases and indicate its role as a regulator of cell behaviour and EV release in breast cancer

Terpene emissions from European beech (Fagus sylvatica L.): Pattern and emission behaviour over two vegetation periods

The source strength of volatile organic compounds (VOCs) emitted by vegetation is of great interest for the understanding of processes in atmospheric chemistry and climate change. In this study terpene emissions from branches of European beech (Fagus sylvatica L.) were studied in a deciduous forest. Using the branch enclosure technique changes in the emission pattern and the variation of emission rates over the year were investigated over two consecutive vegetation periods. More than 10 monoterpene compounds were found in the emissions, among which sabinene dominates. For most compounds the emission pattern changed only slightly over the year. Interestingly, two compounds tentatively identified as para-cymene and cis-ocimene showed differences in the emission behaviour in late summer compared to the other terpenes. In contrast to previous studies our investigation characterise European beech as a strong emitter. For the main compounds the emission rates changed up to two orders of magnitude as a function of temperature and light over the day. In general, highest emission rates were observed in summer and lowest in fall. A seasonality was characterized by a temperature independent decline of emissions in late summer, resulting in changes of the standard emission rate on the order of one magnitude. A standard emission factor of up to 3.5 nmol m(-2)s(-1) for the sum of measured terpenes was calculated. No emissions were found in early spring even though leaves were fully developed and temperature and light conditions were moderate. The results underline the importance of characterising the annual variation of the emission behaviour. Especially for the up-scaling to global VOC emissions, seasonal influences have to be considered to achieve realistic emission inventories