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Environmental Measurements Methods 2
New perspectives on CO, temperature and light effects on BVOC emissions using online measurements by PTR-MS and cavity ring-down spectroscopy Jianbei Huang, Henrik Hartmann, Heidi Hellén, Armin Wisthaler, Erica Perreca, Alexander Weinhold, Alexander Rücker, Nicole M. van Dam, Jonathan Gershenzon, Susan E. Trumbore, and Thomas Behrendt Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.8b01435 • Publication Date (Web): 18 Oct 2018 Downloaded from http://pubs.acs.org on October 19, 2018
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Environmental Science & Technology
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New perspectives on CO2, temperature and light effects on BVOC emissions
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using online measurements by PTR-MS and cavity ring-down spectroscopy
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Authors:
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Jianbei Huang *1, Henrik Hartmann 1, Heidi Hellén 2, Armin Wisthaler 3, Erica Perreca 4,
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Alexander Weinhold
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Gershenzon 4, Susan Trumbore 1, and Thomas Behrendt *1
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Affiliations:
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1
Max-Planck-Institute for Biogeochemistry, Jena, Germany
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2
Finnish Meteorological Institute, Helsinki, Finland
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Department of Chemistry, University of Oslo, Oslo, Norway
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Max Planck Institute for Chemical Ecology, Jena, Germany
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German Centre for Integrative Biodiversity Research, Leipzig, Germany
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Institute of Ecology, Friedrich Schiller University, Jena, Germany
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Alexander Rücker1, Nicole M. van Dam
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Address: Hans-Knöll-Str. 10, 07745 Jena, Thuringia, Germany
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Jonathan
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Abstract
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Volatile organic compounds (VOC) play important roles in atmospheric chemistry, plant ecology
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and physiology, and biogenic VOC (BVOC) emitted by plants is the largest VOC source. Our
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knowledge about how environmental drivers (e.g. carbon, light and temperature) may regulate
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BVOC emissions is limited because they are often not controlled. We combined a greenhouse
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facility to manipulate atmospheric CO2 ([CO2]) with proton-transfer-reaction mass spectrometry
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(PTR-MS) and cavity ring-down spectroscopy to investigate the regulation of BVOC in Norway
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spruce. Our results indicate a direct relationship between [CO2] and methanol and acetone
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emissions, and their temperature and light dependencies, possibly related to substrate
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availability. The composition of monoterpenes stored in needles remained constant, but
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emissions of mono- (linalool) and sesquiterpenes (β-farnesene) increased at lower [CO2], with
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the effects being most pronounced at the highest air temperature. Pulse-labeling suggested an
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immediate incorporation of recently assimilated carbon into acetone, mono- and sesquiterpene
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emissions even under 50 ppm [CO2]. Our results provide new perspectives on CO2, temperature
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and light effects on BVOC emissions, in particular how they depend on stored pools and recent
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photosynthetic products. Future studies using smaller but more seedlings may allow sufficient
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replication to examine the physiological mechanisms behind the BVOC responses.
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Key words: BVOC, CO2, carbon limitation and starvation, defense, monoterpenes, nonstructural
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carbohydrates, Picea abies, secondary metabolites
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Introduction
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Volatile organic compounds (VOC) play important roles in atmospheric chemistry and climate
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by altering the oxidative capacity of the atmosphere,1-3 ozone production in the presence of
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NOx (NO+NO2),4 and the formation of secondary organic aerosols.5 Biogenic VOC (BVOC) is the
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largest VOC source, representing up to ~90% of total emissions.6 However, our limited
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understanding of the function and regulation of BVOC results in large uncertainties in
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estimating and predicting BVOC emissions.7, 8
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Temperature and light are commonly viewed as key environmental factors controlling BVOC
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emissions.6 A rise in the mean global temperature of ~2-3 °C is expected to increase total BVOC
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emissions by 30-45%.9 In global vegetation models such as ORCHIDEE,10 light intensity is the
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main driver of the emissions, accounting for 80% and 60% of methanol and monoterpenes,
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repectively. However, changing atmospheric [CO2] may also affect BVOC emissions, as
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increasing [CO2] from low (~ 190 ppm) to high (~ 600 ppm) has been shown to suppress
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isoprene emissions.11, 12 While such mechanisms that give rise to isoprene emissions have been
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implemented in models,13,14 the information on the physiological regulation of other BVOC
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emissions, e.g. mono- and sesquiterpenes as well as oxygenated BVOC, is still limited.
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Mono- and sesquiterpenes serve important biological and ecological functions, such as
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repelling herbivores and attracting their predators,15 or scavenging harmful reactive oxygen
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species (ROS) in plants.16 Hence, their emissions are often induced by biotic and abiotic stresses
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such as herbivory, intense light and high temperature. 17, 18 It remains unclear whether emitted
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monoterpenes are released from stored pools or synthesized de novo. Data on the third group
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of isoprenoids, sesquiterpenes, are still sparse because these compounds degrade rapidly due
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to their high chemical reactivity with radicals (e.g. hydroxyl radical, OH) and ozone (O3).19, 20
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Plants also emit large quantities of oxygenated VOC (e.g. methanol and acetone) into the
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atmosphere.10, 21 Methanol is thought to be a by-product of pectin demethylation during cell
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wall extension,22,
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including glucose and sucrose are required for pectin synthesis,25 which may play an important
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role in regulating methanol emissions.26 The metabolic pathways involved in the synthesis of
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acetone are not yet fully understood, but it is likely that acetone is produced via pyruvate
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metabolism.27 Field observations demonstrate that emissions of methanol and acetone are
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temperature- and light-dependent,28-30 but their dependence on carbon has received less
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attention. In particular, quantification of interactions between temperature, light and [CO2] on
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emissions and dynamics of these fluxes are still not well understood.
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and is therefore often used as an indicator of growth.24 Saccharides
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To fill this gap, we constructed a greenhouse facility specifically designed to induce
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contrasting carbon availability, spanning very low to ambient [CO2] concentrations (400, 180
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and 50 ppm). We combined proton transfer reaction mass spectrometry (PTR-MS) with gas
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chromatography mass spectrometry (GC-MS) to investigate emissions of terpenoids and
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oxygenated BVOC from whole-canopies (including stem, branches and needles) of 8-year-old
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Norway spruce (Picea abies). We also monitored CO2 and water vapour gas exchange, air
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temperature, and photosynthetically active radiation (PAR) to investigate their relationships to
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BVOC emissions. Concentrations of metabolites including soluble sugars and monoterpenes in
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tissues were measured to investigate the role of substrate availability in BVOC emissions.
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Isotope labelling allows partitioning the contribution of stored pools and recent photosynthetic
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products to BVOC emissions. Such an approach has been successfully applied for determining
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carbon source for isoprene emissions under different [CO2],31-33 and monoterpene emissions
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following herbivory.34 Hence, we also employed 13CO2 pulse-labeling and traced labeled C into
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emissions of acetone, mono- and sesquiterpenes in all [CO2] treatments.
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Materials and Methods
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Plant material
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We conducted two experiments, one in 2016 (experiment I) one and 2017 (experiment II) using
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two genotypes of 8-year-old Norway Spruce saplings (S21K0420117 and S21K04200232 from
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Sweden). Prior to each experiment, trees were grown outdoors in pots filled with sand and a
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slow-releasing fertilizer (Osmocote Start, Everris International B.V., Netherlands). All saplings
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were pruned in July 2015 to make them fit into the growth chambers and were watered
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regularly before the start of the experiment.
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Growth chambers
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Four cylindrical chambers (height=70 cm, diameter=70 cm, volume=270 L) covered with
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fluorinated ethylene propylene (FEP) foil were built to enclose the whole aboveground portion
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of the spruce saplings (Figure S1). Previous studies found that FEP foil transmits about 95 % of
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photosynthetically active radiation (PAR, 400-700 nm) and about 90 % for wavelengths < 400
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nm.35, 36 Four FEP chambers were placed side-by-side on a greenhouse table and three of these
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were used to grow spruce clones. The fourth chamber served as a plant-free reference
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chamber to measure the VOC derived from the incoming air, chemical reactions in the gas
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phase, and adsorption/desorption to the walls of the chamber and tubing.35 Previous work has
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shown that these spruce clones have little differences in concentrations of soluble sugars and
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monotperenes at the whole aboveground level (Figure S2). Except monoterpene emissions
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were induced by tissue damage during transferring trees and sampling, there were little
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differences in emissions of methanol, acetone, and sesquiterpenes (Figure S3). Each chamber
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was flushed continuously through perforated Teflon tubing located at the bottom and an outlet
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at the top of the chamber. A light/dark regime of 16/8 h was maintained using supplemental
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greenhouse lamps (Son-T Agro® 430W HPS bulbs, primary light range = 520–610 nm, Philips®
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Lighting Co., Somerset, NJ, USA) in 2016 and changed to LED lamps (Ultra violet,
