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Down-regulation of photosynthesis and its relation to changes in leaf N allocation and N availability under elevated CO2 after long-term exposure
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  • Siyeon Byeon,
  • Wookyung Song,
  • Minjee Park,
  • Sukyung Kim,
  • HoonTaek Lee,
  • Jihyeon Jeon,
  • Minsu Lee,
  • Hyemin Lim,
  • SimHee Han,
  • ChangYoung Oh,
  • Hyun-Seok Kim
Siyeon Byeon
Seoul National University
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Wookyung Song
National Institute of Forest Science
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Minjee Park
Purdue University
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Sukyung Kim
Seoul National University
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HoonTaek Lee
National Institute of Forest Science
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Jihyeon Jeon
Seoul National University
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Minsu Lee
Seoul National University
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Hyemin Lim
Rural Development Administration
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SimHee Han
National Institute of Forest Science
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ChangYoung Oh
National Institute of Forest Science
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Hyun-Seok Kim
Seoul National University, Seoul National University
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Abstract

Down-regulation of photosynthesis in elevated CO2 (eCO2), could be attributed to depletions in nitrogen (N) availability after long term exposure to eCO2 (progressive nitrogen limitation, PNL) or N dilution due to excessive carbon accumulation of nonstructural carbohydrates. To investigate this, we examined N availability, photosynthetic characteristics, and leaf N allocation in Pinus densiflora, Fraxinus rhynchophylla, and Sorbus alnifolia, grown under three different CO2 concentrations, ambient CO2 (aCO2), aCO2 × 1.4 ppm (eCO21.4), and aCO2 × 1.8 ppm (eCO21.8), for 9 years. N availability increased under eCO21.8, and its allocation to chlorophyll (NFchl) and photosynthetic N use efficiency also increased under eCO2. The maximum carboxylation rate, leaf N per mass (Nmass), and N allocation to Rubisco (NFRub), however, were all lower under eCO21.8. There were interactions in NFchl between canopy × species × CO2 concentrations. The greatest changes in N allocation under eCO2 were in the lower canopy of S. alnifolia, the most shade-tolerant species and this species have relatively high flexibility in N operations compared to shade-intolerant species. Based on the reduction in Nmass that was diluted by increased nonstructural carbohydrates and increased N availability, down-regulation of photosynthesis was found to be caused by the dilution and change in N allocations, rather than PNL.

Peer review status:UNDER REVIEW

08 May 2020Submitted to Plant, Cell & Environment
11 May 2020Assigned to Editor
11 May 2020Submission Checks Completed
29 May 2020Review(s) Completed, Editorial Evaluation Pending