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

N.P.R. Anten, T. Hirose, Y. Onoda, T. Kinugasa, H.Y. Kim, M. Okada, K. Kobayashi

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Abstract

Here we analysed the effects of CO2 (C-a) 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 C-a (c. 200 mumol 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 (P-max) and apparent quantum yields than ambient plants, when measured at their own growth CO2. C-a elevation reduced the total leaf N in the canopy (N-leaf) but had no effect on LAI, and the average leaf N content (N-leaf/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 N-leaf under elevated than under ambient C-a. This indicates that there is an N x C-a 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 C-a elevation.
Original languageEnglish
Pages (from-to)459-471
JournalNew Phytologist
Volume161
Issue number2
DOIs
Publication statusPublished - 2004

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Keywords

  • leaf-area
  • atmospheric co2
  • use efficiency
  • plant-growth
  • photosynthesis
  • dioxide
  • responses
  • leaves
  • nutrition
  • stands

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