title: Short-term water stress impacts on stomatal, mesophyll and biochemical limitations to photosynthesis differ consistently among tree species from contrasting climates.
abstract: Predicting the large-scale consequences of drought in contrasting environments requires that we understand how drought effects differ among species originating from those environments. A previous meta-analysis of published experiments suggested that the effects of drought on both stomatal and non-stomatal limitations to photosynthesis may vary consistently among species from different hydroclimates. Here, we explicitly tested this hypothesis with two short-term water stress experiments on congeneric mesic and xeric species. One experiment was run in Australia using Eucalyptus species and the second was run in Spain using Quercus species as well as two more mesic species. In each experiment, plants were grown under moist conditions in a glasshouse, then deprived of water, and gas exchange was monitored. The stomatal response was analysed with a recently developed stomatal model, whose single parameter g1 represents the slope of the relationship between stomatal conductance and photosynthesis. The non-stomatal response was partitioned into effects on mesophyll conductance (gm), the maximum Rubisco activity (Vcmax) and the maximum electron transport rate (Jmax). We found consistency among the drought responses of g1, gm, Vcmax and Jmax, suggesting that drought imposes limitations on Rubisco activity and RuBP regeneration capacity concurrently with declines in stomatal and mesophyll conductance. Within each experiment, the more xeric species showed relatively high g1 under moist conditions, low drought sensitivity of g1, gm, Vcmax and Jmax, and more negative values of the critical pre-dawn water potential at which Vcmax declines most steeply, compared with the more mesic species. These results indicate adaptive interspecific differences in drought responses that allow xeric tree species to continue transpiration and photosynthesis for longer during periods without rain.
authors.affiliation: Department of Biological Sciences, Macquarie University, NSW 2109, Australia shuangxi.zhou@students.mq.edu.au.
authors.forename: Shuangxi
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Department of Biological Sciences, Macquarie University, NSW 2109, Australia.
authors.forename: Belinda
authors.initials: B
authors.lastname: Medlyn
authors.affiliation: Ecology Department, University of Barcelona, Avgda Diagonal 643, 08028 Barcelona, Spain CREAF (Centre de Recerca Ecològica i Aplicacions Forestals), Universitat Autònoma de Barcelona, 08193 Barcelona, Spain.
authors.forename: Santiago
authors.initials: S
authors.lastname: Sabaté
authors.affiliation: Ecology Department, University of Barcelona, Avgda Diagonal 643, 08028 Barcelona, Spain CREAF (Centre de Recerca Ecològica i Aplicacions Forestals), Universitat Autònoma de Barcelona, 08193 Barcelona, Spain.
authors.forename: Dominik
authors.initials: D
authors.lastname: Sperlich
authors.affiliation: Department of Biological Sciences, Macquarie University, NSW 2109, Australia AXA Chair of Biosphere and Climate Impacts, Grand Challenges in Ecosystems and the Environment and Grantham Institute-Climate Change and the Environment, Department of Life Sciences, Imperial College London, Silwood Park, Buckhurst Road, Ascot SL5 7PY, UK.
authors.forename: I Colin
authors.initials: IC
authors.lastname: Prentice
mesh_terms: D029661:Alnus / Q000502:physiology; D002980:Climate; D003681:Dehydration; D005052:Eucalyptus / Q000502:physiology; D031661:Fraxinus / Q000502:physiology; D058503:Mesophyll Cells / Q000502:physiology; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology*; D054046:Plant Stomata / Q000502:physiology; D018526:Plant Transpiration; D029963:Quercus / Q000502:physiology; D014197:Trees / Q000502:physiology*
keywords: Jmax; Vcmax.; drought sensitivity; gas exchange; hydroclimate; mesophyll conductance; model; stomatal conductance