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This article in AJ

  1. Vol. 98 No. 2, p. 354-381
    Received: Mar 30, 2004

    * Corresponding author(s): gwall@uswcl.ars.ag.gov
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Interactive Effects of Elevated Carbon Dioxide and Drought on Wheat

  1. G. W. Wall *a,
  2. R. L. Garciab,
  3. B. A. Kimballa,
  4. D. J. Hunsakera,
  5. P. J. Pintera,
  6. S. P. Longc,
  7. C. P. Osborned,
  8. D. L. Hendrixe,
  9. F. Wechsungf,
  10. G. Wechsungg,
  11. S. W. Leavitth,
  12. R. L. LaMortea and
  13. S. B. Idsoa
  1. a G.W. Wall, B.A. Kimball, D.J. Hunsaker, P.J. Pinter, Jr., R.L. LaMorte, and S.B. Idso (retired), USDA-ARS, U.S. Water Conservation Lab., 4331 E. Broadway Rd., Phoenix, AZ 85040
    b LI-COR, P.O. Box 4425, Lincoln, NE 68504
    c Univ. of Illinois, Dep. of Crop Science and Plant Biology, 1201 W. Gregory Dr., Urbana-Champaign, IL 61801
    d Dep. of Animal and Plant Sciences, Univ. of Sheffield, Sheffield, S10 2TN, UK
    e D.L. Hendrix (retired), USDA-ARS, Western Cotton Research Lab., 4135 E. Broadway Rd., Phoenix, AZ 85040
    f Potsdam Institute for Climate Impact Research, P.O. Box 601203, D-14412 Potsdam, Germany
    g Dep. of Soil Science, Humboldt Univ. of Berlin, Invalidenstrasse 42, 10115 Berlin, Germany
    h Lab. of Tree-Ring Research, Univ. of Arizona, Tucson, AZ, 85721


Atmospheric CO2 concentration (C a) continues to rise. An imperative exists, therefore, to elucidate the interactive effects of elevated C a and drought on plant water relations of wheat (Triticum aestivum L.). A spring wheat (cv. Yecora Rojo) crop was exposed to ambient (Control: 370 μmol mol−1) and free-air CO2 enrichment (FACE: ambient + 180 μmol mol−1) under ample (Wet), and reduced (Dry), water supplies (100 and 50% replacement of evapotranspiration, respectively) over a 2-yr study. Our objective was to characterize and quantify the responses of 26 edaphic, gas exchange, water relations, carbohydrate pool dynamics, growth, and development parameters to rising C a and drought. Increasing C a minimized the deleterious effects of soil–water depletion by increasing drought avoidance (i.e., lower stomatal conductance and transpiration rate, and growth and development of a more robust root system) and drought tolerance (i.e., enhanced osmoregulation and adaptation of tissue) mechanisms, resulting in a 30% reduction in water stress–induced midafternoon depressions in net assimilation rate. An elevated C a–based increase in daily and seasonal carbon gain resulted in a positive feedback between source capacity (shoots) and sink demand (roots). Devoid of a concomitant rise in global temperature resulting from the rise in C a, improved water relations for a herbaceous, cool-season, annual, C3 cereal monocot grass (i.e., wheat) are anticipated in a future high-CO2 world. These findings are applicable to other graminaceous species of a similar function-type as wheat common to temperate zone grassland prairies and savannas, especially under dryland conditions.

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