Light inhibition of leaf respiration in field-grown Eucalyptus saligna in whole-tree chambers under elevated atmospheric CO2 and summer drought

Authors

  • KRISTINE Y. CROUS,

    1. Division of Plant Sciences, Research School of Biology, Building 46, The Australian National University, Canberra, ACT 0200, Australia
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  • JOANA ZARAGOZA-CASTELLS,

    1. School of Geosciences, University of Edinburgh, Drummond Street, Edinburgh EH8 9XP, UK
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  • DAVID S. ELLSWORTH,

    1. Hawkesbury Institute for the Environment, University of Western Sydney, Hawkesbury Campus, Locked Bag 1797, Penrith, NSW 2751, Australia
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  • REMKO A. DUURSMA,

    1. Hawkesbury Institute for the Environment, University of Western Sydney, Hawkesbury Campus, Locked Bag 1797, Penrith, NSW 2751, Australia
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  • MARKUS LÖW,

    1. Hawkesbury Institute for the Environment, University of Western Sydney, Hawkesbury Campus, Locked Bag 1797, Penrith, NSW 2751, Australia
    2. Melbourne School of Land and Environment, Department of Forest and Ecosystem Science, University of Melbourne, Water St, Creswick, Vic. 3363, Australia
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  • DAVID T. TISSUE,

    1. Hawkesbury Institute for the Environment, University of Western Sydney, Hawkesbury Campus, Locked Bag 1797, Penrith, NSW 2751, Australia
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  • OWEN K. ATKIN

    Corresponding author
    1. Division of Plant Sciences, Research School of Biology, Building 46, The Australian National University, Canberra, ACT 0200, Australia
      O. K. Atkin. Fax: +61 2 61255095; e-mail: Owen.Atkin@anu.edu.au
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O. K. Atkin. Fax: +61 2 61255095; e-mail: Owen.Atkin@anu.edu.au

SUMMARY

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 [CO2] and summer drought. Associated with month-to-month changes in temperature were concomitant changes in R in the light (Rlight) and darkness (Rdark), with both processes being more temperature dependent in well-watered trees than under drought. Overall rates of Rlight and Rdark were not significantly affected by [CO2]. By contrast, overall rates of Rdark (averaged across both [CO2]) 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 Rlight and Rdark when data from all months/treatments were combined (R2 = 0.8). Variations in Rlight 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/Asat). 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.

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