title: Onset of photosynthesis in spring speeds up monoterpene synthesis and leads to emission bursts.
abstract: Emissions of biogenic volatile organic compounds (BVOC) by boreal evergreen trees have strong seasonality, with low emission rates during photosynthetically inactive winter and increasing rates towards summer. Yet, the regulation of this seasonality remains unclear. We measured in situ monoterpene emissions from Scots pine shoots during several spring periods and analysed their dynamics in connection with the spring recovery of photosynthesis. We found high emission peaks caused by enhanced monoterpene synthesis consistently during every spring period (monoterpene emission bursts, MEB). The timing of the MEBs varied relatively little between the spring periods. The timing of the MEBs showed good agreement with the photosynthetic spring recovery, which was studied with simultaneous measurements of chlorophyll fluorescence, CO2 exchange and a simple, temperature history-based proxy for state of photosynthetic acclimation, S. We conclude that the MEBs were related to the early stages of photosynthetic recovery, when the efficiency of photosynthetic carbon reactions is still low whereas the light harvesting machinery actively absorbs light energy. This suggests that the MEBs may serve a protective functional role for the foliage during this critical transitory state and that these high emission peaks may contribute to atmospheric chemistry in the boreal forest in springtime.
authors: SMEAR II Station, University of Helsinki, Korkeakoski, 35500, Finland.|Department of Forest Sciences, University of Helsinki, Helsinki, 00014, Finland.
authors: J
authors: J
authors: Aalto
authors: Department of Forest Sciences, University of Helsinki, Helsinki, 00014, Finland.
authors: A
authors: A
authors: Porcar-Castell
authors: Department of Forest Sciences, University of Helsinki, Helsinki, 00014, Finland.
authors: J
authors: J
authors: Atherton
authors: Department of Forest Sciences, University of Helsinki, Helsinki, 00014, Finland.|Department of Physics, University of Helsinki, Helsinki, 00014, Finland.
authors: P
authors: P
authors: Kolari
authors: SMEAR II Station, University of Helsinki, Korkeakoski, 35500, Finland.
authors: T
authors: T
authors: Pohja
authors: Department of Forest Sciences, University of Helsinki, Helsinki, 00014, Finland.
authors: P
authors: P
authors: Hari
authors: Department of Forest Sciences, University of Helsinki, Helsinki, 00014, Finland.
authors: E
authors: E
authors: Nikinmaa
authors: Department of Physics, University of Helsinki, Helsinki, 00014, Finland.
authors: T
authors: T
authors: Petäjä
authors: Department of Forest Sciences, University of Helsinki, Helsinki, 00014, Finland.
authors: J
authors: J
authors: Bäck
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D039821:Monoterpenes / Q000378:metabolism*; D010788:Photosynthesis; D041605:Pinus sylvestris / Q000378:metabolism*; D012621:Seasons; D013696:Temperature
chemical_list: D039821:Monoterpenes; D002734:Chlorophyll; D002245:Carbon Dioxide
keywords: BVOC; chlorophyll fluorescence; hybrid algorithm; monoterpene emission; spring recovery