Elevated CO2 and nitrogen availability have interactive effects on canopy carbon gain in rice

Authors

  • N. P. R. Anten,

    Corresponding author
    1. Department of Ecology and Evolutionary Biology, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980–8578;
    2. Chair Group of Production Systems, Wageningen University, Haarweg 333 6709 R2, The Netherlands;
    3. Present address: Department of Plant Sciences, Utrecht University, PO Box 800.84 NL-3508, TB Utrecht, The Netherlands
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  • T. Hirose,

    1. Department of Ecology and Evolutionary Biology, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980–8578;
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  • Y. Onoda,

    1. Department of Ecology and Evolutionary Biology, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980–8578;
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  • T. Kinugasa,

    1. Department of Ecology and Evolutionary Biology, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980–8578;
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  • H. Y. Kim,

    1. Japan Science and Technology Cooperation, Tohoku National Agricultural Station, 4 Akahira, Shimikuriyagawa, Morioka, 020-0198;
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  • M. Okada,

    1. Japan Science and Technology Cooperation, Tohoku National Agricultural Station, 4 Akahira, Shimikuriyagawa, Morioka, 020-0198;
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  • K. Kobayashi

    1. National Institute of Agro-Environmental Sciences, 3-1-1 Kannondai, Tsukuba, 305-8604, Japan;
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Author for correspondence: N. P. R. Anten Tel: +31 30 253 6845 Fax: +31 30 251 8366 Email: N.Anten@bio.uu.nl

Summary

  • • Here we analysed the effects of CO2 (Ca) elevation and nitrogen availability on canopy structure, leaf area index (LAI) and canopy photosynthesis of rice (Oryza sativa).
  • • Rice was grown at ambient and elevated Ca (c. 200 µmol mol−1 above ambient, using the free-air CO2 enrichment, FACE) and at two N availabilities. We measured leaf area, area-based leaf N contents and leaf photosynthesis, and calculated net daily canopy photosynthesis.
  • • FACE plants had higher light-saturated rates of photosynthesis (Pmax) and apparent quantum yields than ambient plants, when measured at their own growth CO2. Ca elevation reduced the total leaf N in the canopy (Nleaf) but had no effect on LAI, and the average leaf N content (Nleaf/LAI) was therefore reduced by 8%. This reduction corresponded well with our model predictions. Leaf area index increased strongly with N availability, which was also consistent with our model.
  • • Calculated canopy photosynthesis increased more strongly with Nleaf under elevated than under ambient Ca. This indicates that there is an N × Ca interactive effect on canopy carbon gain. This interaction was caused by the increase in LAI with N availability, which enhanced the positive effect of the higher quantum yield under Ca elevation.

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