title: Online analysis of volatile organic compound emissions from Sitka spruce (Picea sitchensis).
abstract: Volatile organic compound (VOC) emissions from Sitka spruce (Picea sitchensis Bong.) growing in a range of controlled light and temperature regimes were monitored online with a proton transfer reaction-mass spectrometer (PTR-MS) operating at a temporal resolution of approximately 1 min. Isoprene emissions accounted for an average of more than 70% of measured VOCs and up to 3.5% of assimilated carbon. Emission rates (E) for isoprene correlated closely with photosynthetic photon flux (PPF) and temperature, showing saturation at a PPF of between 300 and 400 micromol m(-2) s(-1) and a maximum between 35 and 38 degrees C. Under standard conditions of 30 degrees C and 1000 micromol m(-2) s(-1) PPF, the mean isoprene E was 13 microg gdm(-1) h(-1), considerably higher than previously observed in this species. Mean E for acetaldehyde, methanol and monoterpenes at 30 degrees C were 0.37, 0.78 and 2.97 microg gdm(-1) h(-1), respectively. In response to a sudden light to dark transition, isoprene E decreased exponentially by > 98% over about 3 h; however, during the first 7 min, this otherwise steady decay was temporarily but immediately depressed to approximately 40% of the pre-darkness rate, before rallying during the following 7 min to rejoin the general downward trajectory of the exponential decay. The sudden sharp fall in isoprene E was mirrored by a burst in acetaldehyde E. The acetaldehyde E maximum coincided with the isoprene E minimum (7 min post-illumination), and ceased when isoprene emissions resumed their exponential decay. The causes of, and linkages between, these phenomena were investigated.
authors.affiliation: Institute of Environmental and Natural Sciences, Lancaster University, Lancaster, LA1 4YQ, U.K.
authors.forename: Sean
authors.initials: S
authors.lastname: Hayward
authors.forename: Akira
authors.initials: A
authors.lastname: Tani
authors.forename: Sue M
authors.initials: SM
authors.lastname: Owen
authors.forename: C Nicholas
authors.initials: CN
authors.lastname: Hewitt
mesh_terms: D000079:Acetaldehyde / Q000378:metabolism; D002070:Butadienes / Q000378:metabolism; D045782:Hemiterpenes / Q000378:metabolism; D008027:Light; D013058:Mass Spectrometry; D000432:Methanol / Q000378:metabolism; D039821:Monoterpenes / Q000378:metabolism; D010420:Pentanes / Q000378:metabolism; D028222:Picea / Q000502:physiology*; D013696:Temperature; D014197:Trees / Q000502:physiology*
chemical_list: D002070:Butadienes; D045782:Hemiterpenes; D039821:Monoterpenes; D010420:Pentanes; C005059:isoprene; D000079:Acetaldehyde; D000432:Methanol