Browsing by Subject "monoterpenes"

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  • Canaval, Eva; Hyttinen, Noora; Schmidbauer, Benjamin; Fischer, Lukas; Hansel, Armin (2019)
    In this study, we present reactions of NH4+ with a series of analytes (A): acetone (C3H6O), methyl vinyl ketone (C4H6O), methyl ethyl ketone (C4H8O) and eight monoterpene isomers (C10H16) using a Selective Reagent Ionization Time-of-Flight Mass Spectrometer (SRI-ToF-MS). We studied the ion-molecule reactions at collision energies of 55 meV and 80 meV. The ketones, having a substantially lower proton affinity than NH3, produce only cluster ions NH4+(A) in detectable amounts at 55 meV. At 80 meV, no cluster ions were detected meaning that these adduct ions are formed by strongly temperature dependent association reactions. Bond energies of cluster ions and proton affinities for most monoterpenes are not known and were estimated by high level quantum chemical calculations. The calculations reveal monoterpene proton affinities, which range from slightly smaller to substantially higher than the proton affinity of NH3. Proton affinities and cluster bond energies allow to group the monoterpenes as a function of the enthalpy for the dissociation reaction . We find that this enthalpy can be used to predict the NH4+-A cluster ion yield. The present study explains product ion formation involving NH4+ ion chemistry. This is of importance for chemical ionization mass spectrometry (CIMS) utilizing NH4+ as well as NH4+(H2O) as reagent ions to quantitatively detect atmospherically important organic compounds in real-time.
  • Rissanen, Kaisa (Helsingfors universitet, 2014)
    As most conifers, pine trees produce and store oleoresin in their resin ducts. Oleoresin is a defensive secondary metabolite that protects trees mainly against bark beetles and herbivores. The oleoresin of pine trees consists of different hydrocarbons, such as terpenes and resin acids. Inside the resin ducts, the pressure of oleoresin varies from 3 to 12 bars depending on the tree species, individual tree and environmental conditions. Traditionally, oleoresin has been studied because of its defensive features, since it has an important role in preventing insect-induced damage in coniferous forest .The pressure of oleoresin in pine trees has been a subject for excessive studies especially in 1960s and 1970s due to large epidemics of bark beetles, for example Dendroctonus frontalis, in United States of America. As a result, oleoresin pressure has been linked to the water balance of a tree. Since the changes in the tension of water inside water conducting tracheids affect the diameter of xylem, the diurnal pattern of oleoresin pressure and the diameter of xylem have been recorded to be similar. The connections between oleoresin pressure and other physiological processes of a tree have nevertheless been neglected, although there may be a strong relation between the pressure of oleoresin and the BVOC (biogenic volatile organic compound) -emissions from the trunk of a tree. The constituents of oleoresin, for example monoterpenes, form a part of the BVOC emissions that pine forests emit. Estimating the BVOC emissions from tree trunks and from forests and understanding the mechanisms behind monoterpene emissions would be essential, because BVOCs have been detected to contribute to the cloud formation and thus to the climate. In addition, the studies on oleoresin pressure are relatively old and conducted mostly in Southern USA where the climate is mainly subtropical. In boreal forests of Northern Europe, the pressure of oleoresin has not been extensively studied before the summer of 2012, when the preliminary study for this study was conducted. The results of the preliminary study were contrary to the earlier studies conducted in Southern USA. The maximum pressures of oleoresin pressure were recorded in the afternoon and minimum pressures before sunrise, whereas according to the literature the pressure of oleoresin is highest in the early morning and lowest in the afternoon. Hence, in this study the diurnal variations in oleoresin pressure of Scots pine (Pinus sylvestris) are measured at the SMEAR II station in Southern Finland. A pressure gauge system similar to that of Vité (1961) and Perrakis (2008) is employed. The variations in oleoresin pressure are compared to environmental variables (temperature, VPD and PAR) and physiological variables (the diameter of xylem, transpiration and photosynthesis). Furthermore, the connection between oleoresin pressure and monoterpene emissions from a pine trunk is analysed by the means of EFRA - approach. The results on the diurnal pattern of oleoresin pressure are throughout the summer of 2013 similar to the results of the preliminary study. The pressure of oleoresin is highest during the warmest time of a day and lowest during the coldest time of a day. According to the results, temperature is the single variable that explains the changes in oleoresin pressure the best. However, temperature fails to explain all the changes in oleoresin pressure, so there appears to be other influences that are outshadowed by the effect of temperature. These influences could be generated by water balance and VPD, as explained in literature, since the diameter of xylem is the single variable that explains best the changes in temperature corrected oleoresin pressure. Furthermore, a relation between monoterpene emissions and oleoresin pressure is detected, although temperature appears to affect both the emissions of monoterpenes and the pressure of oleoresin.
  • Vanhatalo, Anni; Aalto, Juho; Chan, Tommy; Hölttä, Teemu; Kolari, Pasi; Rissanen, Kaisa; Kabiri, Kourosh; Hellén, Heidi; Bäck, Jaana (2020)
    The volatile organic compound (VOC) fluxes of living plant compartments other than foliage are poorly known. In this paper we describe for the first time the methanol and monoterpene fluxes from living Scots pine stems in situ, over 4 years at the SMEAR II station in southern Finland. The VOC fluxes from stems were measured online with an automated chamber measurement system. Both methanol and monoterpene emissions showed strong diurnal and seasonal cycles. Methanol emission rates were highest in mid-summer, and coincided with the most intensive period of stem radial growth. Methanol emission rates correlated moderately with the xylem sap flow rate and foliage transpiration rate, which suggests that many simultaneous and overlapping processes are related to methanol transport and production in trees. Monoterpene emissions from stems were highest on the hottest summer days, but also substantial in winter during times when the temperature was above zero °C for several days. Overall, the emissions from stems constitute about 2% of the whole stand monoterpene emissions under normal, non-stressed conditions. This can be used in stand monoterpene emission models as the rough estimate of woody compartment contribution.