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This article in AJ

  1. Vol. 82 No. 4, p. 834-840
    Received: July 24, 1989

    * Corresponding author(s):
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Rice Photosynthesis and Evapotranspiration in Subambient, Ambient, and Superambient Carbon Dioxide Concentrations

  1. J. T. Baker ,
  2. L. H. Allen,
  3. K. J. Boote,
  4. P. Jones and
  5. J. W. Jones
  1. A gron. Dep., Univ. of Florida, Gainesville, FL 32611
    U SDA-ARS, Bldg. 164, Univ. of Florida, Gainesville, FL 32611



The current global rise in atmospheric carbon dioxide concentration, [CO2], has stimulated interest in the response of agricultural crops to ICO2]. The objectives were to determine the effects of [CO2] on photosynthesis, evapotranspiration, and water use efficiency of rice (Oryza sativa, L., cv. IR-30). Rice plants were grown in naturally sunlit, plant growth chambers in subambient (160 and 250), ambient (330), or superambient (500, 660, and 900 nmol CO2 mol−1 air) |CO2] treatments. Photosynthetic light response curves were analyzed to obtain estimates of canopy light utilization efficiency (α) and canopy conductance to CO2 transfer (τ). Estimates of a increased with increasing [CO2] treatment with the greatest increase in the 160 ito 500 μmol mol−1 treatments. Estimates of τ were more variable tham those for α and were not different among [CO2] treatments. Photosynthetic rates increased with increasing [CO2] treatment from 160 to 500 μmol mol−1 followed by a leveling off of the response among the superambient [CO2] treatments. Evapotranspiration decreased while water-use efficiency increased with increasing [CO2]. Shortterm cross-switching of [CO2] among the chambers revealed a profound adaptive response to long-term [CO2] growth treatments. Photosynthetic rate, measured at a common [CO2], decreased with increasing long-term [CO2] growth treatment. The lack of further Photosynthetic response above the 500 μmol mol−1 [CO2] treatment appears to indicate a need to select or screen rice cultivars for increased response to superambient [CO2] in order to more fully take advantage of future increases in global atmospheric [CO2].

Contribution by the Inst. of Food and Agric. Sci., Univ. of Florida, and the USDA-ARS. Supported in part by the U.S. DOE, Carbon Dioxide Res. Div., Interagency Agreement no. DE-AI01-81ER60001. Florida Agric. Exp. Stn. Journal Series no. R-00058.

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