Volume 15, issue 11 | Copyright
Biogeosciences, 15, 3461-3474, 2018
https://doi.org/10.5194/bg-15-3461-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 11 Jun 2018

Research article | 11 Jun 2018

Thermal acclimation of leaf photosynthetic traits in an evergreen woodland, consistent with the coordination hypothesis

Henrique Fürstenau Togashi1, Iain Colin Prentice1,2, Owen K. Atkin3,4, Craig Macfarlane5, Suzanne M. Prober5, Keith J. Bloomfield3, and Bradley John Evans6 Henrique Fürstenau Togashi et al.
  • 1Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia
  • 2AXA Chair of Biosphere and Climate Impacts, Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot SL5 7PY, UK
  • 3Division of Plant Sciences, Research School of Biology, Australian National University, Canberra, Australia
  • 4ARC Centre of Excellence in Plant Energy Biology, Research School of Biology, Australian National University, Canberra, Australia
  • 5CSIRO Land and Water, Private Bag 5, Wembley WA 6913, Australia
  • 6Faculty of Agriculture and Environment, Department of Environmental Sciences, The University of Sydney, NSW 2006, Sydney, Australia

Abstract. Ecosystem models commonly assume that key photosynthetic traits, such as carboxylation capacity measured at a standard temperature, are constant in time. The temperature responses of modelled photosynthetic or respiratory rates then depend entirely on enzyme kinetics. Optimality considerations, however, suggest this assumption may be incorrect. The coordination hypothesis (that Rubisco- and electron-transport-limited rates of photosynthesis are co-limiting under typical daytime conditions) predicts, instead, that carboxylation (Vcmax) capacity should acclimate so that it increases somewhat with growth temperature but less steeply than its instantaneous response, implying that Vcmax when normalized to a standard temperature (e.g. 25°C) should decline with growth temperature. With additional assumptions, similar predictions can be made for electron-transport capacity (Jmax) and mitochondrial respiration in the dark (Rdark). To explore these hypotheses, photosynthetic measurements were carried out on woody species during the warm and the cool seasons in the semi-arid Great Western Woodlands, Australia, under broadly similar light environments. A consistent proportionality between Vcmax and Jmax was found across species. Vcmax, Jmax and Rdark increased with temperature in most species, but their values standardized to 25°C declined. The ci : ca ratio increased slightly with temperature. The leaf N : P ratio was lower in the warm season. The slopes of the relationships between log-transformed Vcmax and Jmax and temperature were close to values predicted by the coordination hypothesis but shallower than those predicted by enzyme kinetics.

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Ecosystem models commonly assume that photosynthetic traits, such as carboxylation capacity measured at a standard temperature, are constant in time and therefore do not acclimate. Optimality hypotheses suggest this assumption may be incorrect. We investigated acclimation by carrying out measurements on woody species during distinct seasons in Western Australia. Our study shows evidence that carboxylation capacity should acclimate so that it increases somewhat with growth temperature.
Ecosystem models commonly assume that photosynthetic traits, such as carboxylation capacity...
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