Photosynthesis and stomatal conductance responses of poplars to free-air CO2 enrichment (PopFACE) during the first growth cycle and immediately following coppice

Authors

  • C. J. Bernacchi,

    Corresponding author
    1. Photosynthesis Research Unit, Agricultural Research Service, United States Department of Agriculture, Urbana, Illinois 61801, USA:
    2. Departments of Plant Biology and Crop Sciences, University of Illinois, Urbana, Illinois 61801, USA:
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  • C. Calfapietra,

    1. Universitá degli Studi della Tuscia, Department of Forest Environment and Resources (DISAFRI), Via S. Camillo de Lellis, I-01100 Viterbo, Italy;
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  • P. A. Davey,

    1. Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
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  • V. E. Wittig,

    1. Departments of Plant Biology and Crop Sciences, University of Illinois, Urbana, Illinois 61801, USA:
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  • G. E. Scarascia-Mugnozza,

    1. Universitá degli Studi della Tuscia, Department of Forest Environment and Resources (DISAFRI), Via S. Camillo de Lellis, I-01100 Viterbo, Italy;
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  • C. A. Raines,

    1. Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
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  • S. P. Long

    1. Departments of Plant Biology and Crop Sciences, University of Illinois, Urbana, Illinois 61801, USA:
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Author for correspondence: C. J. Bernacchi Tel: +1 (217) 333 3040 Email: bernacch@life.uiuc.edu

Summary

  • •   Using the Poplar Free Air CO2 Enrichement (PopFACE) facility we investigated the effects of elevated [CO2] on the diurnal and growth cycle responses of photosynthesis and conductance in three poplar species.
  • •   In situ diurnal measurements of photosynthesis were made on Populus alba, P. nigra and P. ×euramericana and, in parallel, in vivo maximum capacity for carboxylation (Vc,max) and maximum rates of electron transport (Jmax) were determined by gas exchange measurement.
  • •   Light saturated (Asat) and daily integrated (A′) photosynthesis increased at elevated [CO2] in all species. Elevated [CO2] decreased Vc,max and Jmax for P. nigra and Jmax for P.¥euramericana but had no effect on stomatal conductance in any of the species throughout the first growth cycle. During post-coppice re-growth, elevated [CO2] did not increase Asat in P. nigra and P.×euramericana due to large decreases in Vc,max and Jmax.
  • •   A 50% increase in [CO2] under these open-air field conditions resulted in a large and sustained increase in Asat. Although there were some differences between the species, these had little effect on photosynthetic rates at the growth [CO2]. Nevertheless the results show that even fast growing trees grown without rooting volume restriction in the open may still show some down-regulation of photosynthetic potential at elevated [CO2].

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