98 research outputs found

    Variability of BVOC emissions from a Mediterranean mixed forest in southern France with a focus on Quercus pubescens

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    International audienceWe aimed at quantifying biogenic volatile organic compound (BVOC) emissions in June from three Mediter-ranean species located at the O 3 HP site (southern France): Quercus pubescens, Acer monspessulanum and C. coggygria (for isoprene only). As Q. pubescens was shown to be the main BVOC emitter with isoprene representing ≈ 99 % of the carbon emitted as BVOC, we mainly focused on this species. C. coggygria was found to be a non-isoprene emitter (no other BVOCs were investigated). To fully understand both the canopy effect on Q. pubescens isoprene emissions and the inter-individual variability (tree to tree and within canopy), diurnal variations of isoprene were investigated from nine branches (seven branches located to the top of canopy at ≈ 4 m above ground level (a.g.l.), and two inside the canopy at ≈ 2 m a.g.l.). The Q. pubescens daily mean isoprene emission rate (ER d) fluctuated between 23 and 98 µgC g −1 DM h −1. Q. pubescens daily mean net assimilation (Pn) ranged between 5.4 and 13.8, and 2.8 and 6.4 µmol CO 2 m −2 s −1 for sunlit and shaded branches respectively. Both ER d and isoprene emission factors (Is), assessed according to Guenther et al. (1993) algorithm, varied by a factor of 4.3 among the sunlit branches. While sunlit branches ER d was clearly higher than for shaded branches, there was a non-significant variability of Is (59 to 77 µgC g −1 DM h −1). Diurnal variations of iso-prene emission rates (ERs) for sunlit branches were also investigated. ERs were detected at dawn 2 h after Pn became positive and were mostly exponentially dependent on Pn. Diurnal variations of ERs were not equally well described throughout the day by temperature (C T) and light (C L) parameters according to G93 algorithm. Temperature had more impact than photosynthetically active radiation (PAR) on the morning emissions increase, and ER was no longer correlated to C L × C T between solar noon (maximum ER) and mid-afternoon, possibly due to thermal stress of the plant. A comparison between measured and calculated emissions using two isoprene algorithms (G93 and MEGAN – Model of Emissions of Gases and Aerosols from Nature) highlighted the importance of isoprene emission factor Is value used, and some weakness in assessing isoprene emissions under Mediterranean climate conditions (drought) with current iso-prene models

    Concentrations and fluxes of isoprene and oxygenated VOCs at a French Mediterranean oak forest

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    The CANOPEE project aims to better understand the biosphere–atmosphere exchanges of biogenic volatile organic compounds (BVOCs) in the case of Mediterranean ecosystems and the impact of in-canopy processes on the atmospheric chemical composition above the canopy. Based on an intensive field campaign, the objective of our work was to determine the chemical composition of the air inside a canopy as well as the net fluxes of reactive species between the canopy and the boundary layer. Measurements were carried out during spring 2012 at the field site of the Oak Observatory of the Observatoire de Haute Provence (O3HP) located in the southeast of France. The site is a forest ecosystem dominated by downy oak, Quercus pubescens Willd., a typical Mediterranean species which features large isoprene emission rates. Mixing ratios of isoprene, its degradation products methylvinylketone (MVK) and methacrolein (MACR) and several other oxygenated VOC (OxVOC) were measured above the canopy using an online proton transfer reaction mass spectrometer (PTR-MS), and fluxes were calculated by the disjunct eddy covariance approach. The O3HP site was found to be a very significant source of isoprene emissions, with daily maximum ambient concentrations ranging between 2–16 ppbv inside and 2–5 ppbv just above the top of the forest canopy. Significant isoprene fluxes were observed only during daytime, following diurnal cycles with midday net emission fluxes from the canopy ranging between 2.0 and 9.7 mg m−2 h1. Net isoprene normalized flux (at 30 °C, 1000 μmol quanta m−2 s−1) was estimated at 7.4 mg m−2 h−1. Evidence of direct emission of methanol was also found exhibiting maximum daytime fluxes ranging between 0.2 and 0.6 mg m−2 h−1, whereas flux values for monoterpenes and others OxVOC such as acetone and acetaldehyde were below the detection limit. The MVK+MACR-to-isoprene ratio provided useful information on the oxidation of isoprene, and is in agreement with recent findings proposing weak production yields of MVK and MACR, in remote forest regions where the NOx concentrations are low. In-canopy chemical oxidation of isoprene was found to be weak and did not seem to have a significant impact on isoprene concentrations and fluxes above the canopy

    Proline and glycine betaine accumulation in two succulent halophytes under natural and experimental conditions

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    [EN] Proline (Pro) and glycine betaine (GB) contents were determined in two Mediterranean halophytes, Plantago crassifolia and Inula crithmoides, to assess their possible role in salt tolerance of both taxa. Plant material was collected in a littoral salt marsh under different environmental conditions, and from plants subjected to salt treatments in a growth chamber. Relative growth inhibition by NaCl indicated that I. crithmoides is more salt-tolerant than P. crassifolia, in agreement with the distribution of the two species in nature. Field and laboratory data confirmed GB as the major osmolyte responsible for osmotic adjustment in I. crithmoides, but with only a minor role if any as osmoprotectant in the salt tolerance of P. crassifolia. Under natural conditions, Pro contents were very low in both taxa, but increased to levels high enough to contribute significantly to osmotic balance when plants were artificially treated with 450 600mM NaCl higher salt concentrations than those they would normally encounter in their natural habitats. These data suggest that halophytes possess built-in mechanisms, such as accumulation of additional osmolytes, to rapidly adapt to increasing salinity levels in their natural ecosystems; for example, those expected to be caused by climate change in salt marshes in the Mediterranean region.This work was funded by a grant to O.V. from the Spanish Ministry of Science and Innovation (Project CGL2008-00438/BOS), with contribution from the European Regional Development Fund. COST Action FA0901: "Putting Halophytes to work - From Genes to Ecosystems" supported M. N. Grigore for his stay in Valencia within the frame of a Short-Term Scientific Mission. A. Tifrea was funded by the Erasmus fellowship programme for her stay in Valencia to carry out her Master Thesis.Pardo-Domenech, L.; Tifrea, A.; Grigore, M.; Boscaiu, M.; Vicente, O. (2016). Proline and glycine betaine accumulation in two succulent halophytes under natural and experimental conditions. Plant Biosystems - An International Journal Dealing with all Aspects of Plant Biology. 150(5):904-915. https://doi.org/10.1080/11263504.2014.990943S904915150

    Plaisirs d’amour, sens de la vie

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    Numéro consacré à l’amour, catalogue de l’exposition organisée par le CALinfo:eu-repo/semantics/publishe

    Acte(s) culturel(s) et citoyenneté: en-jeux de l'éducation permanente

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    info:eu-repo/semantics/publishe

    Personne-ressource

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    pour les réflexions finales de la Journée de réflexion et de débat organisée par la Direction générale des affaires culturelles de la Province de Hainautinfo:eu-repo/semantics/nonPublishe

    Ensaios terapêuticos com penicilina: II - Sífilis: (Nota prévia)

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    Seis sifiliticos foram tratados com penicilina em doses baixas, no Hospital Evandro Chagas, do Instituto Oswaldo Cruz. Protossifilomas foram bacterioscópicamente negativos entre 3 e 6 dias e cicatrizaram completamente entre 10 e 13 idas, com a aplicação de 1.200 a 2.400 unidades Oxford por 24 horas. Condilomas sifiliticos e placas mucosas hipertróficos tiveram bacterioscopia negativa entre 6 e 8 dias, cicatrizaram completamente entre 10 e 20 dias, com a aplicação de 1.200 unidades por 24 horas. Porém, doses de 4.800 unidades, no mesmo espaço de tempo, forma insuficientes para controlar outras manifestações luéticas secundárias (roséolas, placas mucosas). Em 3 casos sob contrõle sorológico, verificou-se que a negatividade das reações não acompanha imediatamente a cura clínica. Além disso, conforme já foi observado também com a bouba, os resultados dos testes sorológicos oscilam mezes a fio, negativando e voltando à positividade.<br>Six syphilitic patients were treated with Penicillin in low dosis at the Evandro Chagas Hospital, of the Oswaldo Cruz Insitute. Protosyphilomas were found to be bacterioscopically-negative in between three and six days, and cicatrized completely between 10 and 13 days, under applicatins of 1.200 mucous patches, showed negative bacterioscopical results within between 10 and 20 days, under the applications fo 1.200 Oxford units per 24 hours. Doses of 4.800 units, during the same period of time, however, found insufficient to control other secundary luetic manifestations (roseolar rash). In three cases under sorological control it was found that after a clinical cure had been effected, the Wassermann reaction showed considerable escillation, becoming first negative and then pesitive again
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