title: A model of plant isoprene emission based on available reducing power captures responses to atmospheric CO₂.
abstract: We present a unifying model for isoprene emission by photosynthesizing leaves based on the hypothesis that isoprene biosynthesis depends on a balance between the supply of photosynthetic reducing power and the demands of carbon fixation. We compared the predictions from our model, as well as from two other widely used models, with measurements of isoprene emission from leaves of Populus nigra and hybrid aspen (Populus tremula × P. tremuloides) in response to changes in leaf internal CO2 concentration (C(i)) and photosynthetic photon flux density (PPFD) under diverse ambient CO2 concentrations (C(a)). Our model reproduces the observed changes in isoprene emissions with C(i) and PPFD, and also reproduces the tendency for the fraction of fixed carbon allocated to isoprene to increase with increasing PPFD. It also provides a simple mechanism for the previously unexplained decrease in the quantum efficiency of isoprene emission with increasing C(a). Experimental and modelled results support our hypothesis. Our model can reproduce the key features of the observations and has the potential to improve process-based modelling of isoprene emissions by land vegetation at the ecosystem and global scales.
authors.affiliation: Department of Life Sciences, Imperial College, Silwood Park, Ascot, SL5 7PY, UK.
authors.forename: Catherine
authors.initials: C
authors.lastname: Morfopoulos
authors.forename: Dominik
authors.initials: D
authors.lastname: Sperlich
authors.forename: Josep
authors.initials: J
authors.lastname: Peñuelas
authors.forename: Iolanda
authors.initials: I
authors.lastname: Filella
authors.forename: Joan
authors.initials: J
authors.lastname: Llusià
authors.forename: Belinda E
authors.initials: BE
authors.lastname: Medlyn
authors.forename: Ülo
authors.initials: Ü
authors.lastname: Niinemets
authors.forename: Malcolm
authors.initials: M
authors.lastname: Possell
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Sun
authors.forename: Iain Colin
authors.initials: IC
authors.lastname: Prentice
mesh_terms: D002070:Butadienes; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D045782:Hemiterpenes / Q000096:biosynthesis*; D008954:Models, Biological; D010420:Pentanes; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology; D032107:Populus / Q000502:physiology*
chemical_list: D002070:Butadienes; D045782:Hemiterpenes; D010420:Pentanes; C005059:isoprene; D002245:Carbon Dioxide; D002244:Carbon
keywords: black poplar (Populus nigra); hybrid aspen (Populus tremula × P. tremuloides); isoprene emission; light response; modelling; photosynthetic electron transport; quantum yield; volatile compounds