title: Light inhibition of leaf respiration in field-grown Eucalyptus saligna in whole-tree chambers under elevated atmospheric CO2 and summer drought.
abstract: We investigated whether the degree of light inhibition of leaf respiration (R) differs among large Eucalyptus saligna grown in whole-tree chambers and exposed to present and future atmospheric [CO(2) ] and summer drought. Associated with month-to-month changes in temperature were concomitant changes in R in the light (R(light) ) and darkness (R(dark) ), with both processes being more temperature dependent in well-watered trees than under drought. Overall rates of R(light)  and R(dark)  were not significantly affected by [CO(2) ]. By contrast, overall rates of R(dark)  (averaged across both [CO(2) ]) were ca. 25% lower under drought than in well-watered trees. During summer, the degree of light inhibition of leaf R was greater in droughted (ca. 80% inhibition) than well-watered trees (ca. 50% inhibition). Notwithstanding these treatment differences, an overall positive relationship was observed between R(light)  and R(dark)  when data from all months/treatments were combined (R(2)  = 0.8). Variations in R(light)  were also positively correlated with rates of Rubisco activity and nitrogen concentration. Light inhibition resulted in a marked decrease in the proportion of light-saturated photosynthesis respired (i.e. reduced R/A(sat) ). Collectively, these results highlight the need to account for light inhibition when assessing impacts of global change drivers on the carbon economy of tree canopies.
authors.affiliation: Division of Plant Sciences, Research School of Biology, Building 46, The Australian National University, Canberra, ACT 0200, Australia.
authors.forename: Kristine Y
authors.initials: KY
authors.lastname: Crous
authors.forename: Joana
authors.initials: J
authors.lastname: Zaragoza-Castells
authors.forename: David S
authors.initials: DS
authors.lastname: Ellsworth
authors.forename: Remko A
authors.initials: RA
authors.lastname: Duursma
authors.forename: Markus
authors.initials: M
authors.lastname: Löw
authors.forename: David T
authors.initials: DT
authors.lastname: Tissue
authors.forename: Owen K
authors.initials: OK
authors.lastname: Atkin
mesh_terms: D001315:Australia; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D019069:Cell Respiration; D003624:Darkness; D055864:Droughts; D005052:Eucalyptus / Q000378:metabolism* / Q000528:radiation effects*; D008027:Light; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism; D055668:Photochemical Processes / Q000528:radiation effects; D010788:Photosynthesis / Q000528:radiation effects*; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D054046:Plant Stomata / Q000378:metabolism / Q000528:radiation effects; D018526:Plant Transpiration / Q000528:radiation effects; D012273:Ribulose-Bisphosphate Carboxylase / Q000032:analysis / Q000378:metabolism; D012621:Seasons; D013312:Stress, Physiological; D013696:Temperature; D014197:Trees; D014867:Water
chemical_list: D014867:Water; D002245:Carbon Dioxide; D002244:Carbon; D012273:Ribulose-Bisphosphate Carboxylase; D009584:Nitrogen