title: Linking photosynthesis and leaf N allocation under future elevated CO2 and climate warming in Eucalyptus globulus.
abstract: Leaf-level photosynthetic processes and their environmental dependencies are critical for estimating CO2 uptake from the atmosphere. These estimates use biochemical-based models of photosynthesis that require accurate Rubisco kinetics. We investigated the effects of canopy position, elevated atmospheric CO2 [eC; ambient CO2 (aC)+240 ppm] and elevated air temperature (eT; ambient temperature (aT)+3 °C) on Rubisco content and activity together with the relationship between leaf N and Vcmax (maximal Rubisco carboxylation rate) of 7 m tall, soil-grown Eucalyptus globulus trees. The kinetics of E. globulus and tobacco Rubisco at 25 °C were similar. In vitro estimates of Vcmax derived from measures of E. globulus Rubisco content and kinetics were consistent, although slightly lower, than the in vivo rates extrapolated from gas exchange. In E. globulus, the fraction of N invested in Rubisco was substantially lower than for crop species and varied with treatments. Photosynthetic acclimation of E. globulus leaves to eC was underpinned by reduced leaf N and Rubisco contents; the opposite occurred in response to eT coinciding with growth resumption in spring. Our findings highlight the adaptive capacity of this key forest species to allocate leaf N flexibly to Rubisco and other photosynthetic proteins across differing canopy positions in response to future, warmer and elevated [CO2] climates.
authors.affiliation: Research School of Biology, Australian National University, Canberra, ACT 2601, Australia.|ARC Centre of Excellence for Translational Photosynthesis, Australia.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Sharwood
authors.affiliation: Hawkesbury Institute for the Environment, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia.
authors.forename: Kristine Y
authors.initials: KY
authors.lastname: Crous
authors.affiliation: Research School of Biology, Australian National University, Canberra, ACT 2601, Australia.|ARC Centre of Excellence for Translational Photosynthesis, Australia.
authors.forename: Spencer M
authors.initials: SM
authors.lastname: Whitney
authors.affiliation: Hawkesbury Institute for the Environment, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia.
authors.forename: David S
authors.initials: DS
authors.lastname: Ellsworth
authors.affiliation: ARC Centre of Excellence for Translational Photosynthesis, Australia.|Hawkesbury Institute for the Environment, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia.
authors.forename: Oula
authors.initials: O
authors.lastname: Ghannoum
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D002980:Climate; D057231:Climate Change; D005052:Eucalyptus / Q000378:metabolism*; D009517:New South Wales; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase
chemical_list: D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase
keywords: Canopy position; Eucalyptus globulus; Rubisco kinetics; Vcmax; elevated CO2 and temperature; photosynthesis; whole-tree chambers.