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This article in JEQ

  1. Vol. 28 No. 3, p. 880-887
     
    Received: Dec 22, 1997


    * Corresponding author(s): brett.runion@ipaper.com
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doi:10.2134/jeq1999.00472425002800030020x

Longleaf Pine Photosynthetic Response to Soil Resource Availability and Elevated Atmospheric Carbon Dioxide

  1. G. B. Runion *,
  2. R. J. Mitchell,
  3. T. H. Green,
  4. S. A. Prior,
  5. H. H. Rogers and
  6. D. H. Gjerstad
  1. I nternational Paper, 719 Southlands Road, Bainbridge, GA 31717;
    J W. Jones Ecological Research Center, Route 2, Box 2324, Newton, GA 31770;
    D ep. of Plant and Soil Science, P.O. Box 1208, Alabama A&M Univ., Normal, AL 35762;
    S chool of Forestry, 108 M. White Smith Hall, Auburn Univ., AL 36849.

Abstract

Abstract

Gas exchange responses during a drought cycle were studied in longleaf pine (Pinus palustris Mill.) seedlings after prolonged exposure to varying levels of atmospheric CO2 (≈365 or ≈730 µmol CO2 mol−1), soil N (40 or 400 kg N ha−1 yr−1), and water (“adequate” and “stressed”). Elevated atmospheric CO2 concentration increased photosynthesis, tended to decrease stomatal conductance, and increased water-use efficiency (WUE). Although soil resource availability influenced gas exchange measurements, it generally did not affect the magnitude or direction of the response to CO2 concentration. However, significant interactions among treatment variables were observed for plant xylem pressure potential. In seedlings grown with high N, a positive growth response to elevated atmospheric CO2 increased whole-plant water use resulting in more severe plant water stress, despite increased leaf-level WUE; however, under low N conditions the lack of a growth response to elevated CO2 reduced whole-plant water use, decreased water stress severity, and increased WUE. Photosynthetic response to CO2 was greatest in the high N treatment at the beginning of the drought cycle, but diminished as water stress increased; however, plants grown with low N showed greater photosynthetic responses to CO2 later in the drought cycle. Therefore, plant gas exchange rates interact with growth response in determining the severity of water stress under drought and, thus, the ability of elevated atmospheric CO2 to ameliorate the effects of drought and allow plants to maintain increased rates of photosynthesis may be influenced by the availability of other resources, such as N and water.

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