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Crop Science Abstract -

Carbon Isotope Discrimination: Relationship to Yield, Gas Exchange, and Water-Use Efficiency in Field-Grown Crested Wheatgrass


This article in CS

  1. Vol. 32 No. 1, p. 168-175
    Received: Mar 8, 1991

    * Corresponding author(s):
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  1. John J. Read ,
  2. Douglas A. Johnson,
  3. Kay H. Asay and
  4. Larry L. Tieszen
  1. U SDA-ARS, Crops Res. Lab., 1701 Center Ave., Fort Collins, CO 80526
    B iology Dep., Augustana College, Sioux Falls, SD 57197



In previous greenhouse experiments, stable C isotope discrimination (Δ) was negatively associated with water-use efficiency (WUE) in crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes]. We conducted two field experiments to evaluate associations among Δ, leaf WUE, and shoot WUE (dry weight change/plant transpiration) in clones of crested wheatgrass selected on the basis of low, medium, or high Δ. The first experiment involved leaves of five clones from each Δ class, with WUEi and Δ determined at two field sites. Mean Δ values are always less for low-Δ than high-Δ clones, but did not differ significantly between medium-Δ and high-Δ clones. Negative correlations were obtained between Δ and WUEi at both the rainfed (r = −0.77**, df = 13, p < 0.01) and irrigated (r = −0.87**, df = 13) sites; however, WUEi of low-Δ clones exceeded that of high-Δ clones only under rainfed conditions. The second experiment compared the performance of three low-Δ and three high-Δ clones under well-watered and draughted conditions. Plants were grown in pots imbedded in soil. Soil water content in the pots was maintained at either 0.16 or 0.06 kg H2O kg−1 soil. Within each water level, values for Δ and leaf intercellular CO2 concentration (ci) were less for low-Δ than high-Δ clones and were negatively associated with both WUEi and WUEs. Even though shoot dry weight and Δ decreased with drought, the two traits were not correlated for either well-watered or droughted clones. Across water levels, Δ was negatively correlated with WUEi (r = −0.93**, df = 10) and with WUEs (r = −0.98**, df = 10). Results show Δ in field-grown crested wheatgrass was consistent across sites and was consistently related to ci, WUEi, and WUEs.

Joint contribution of the USDA-ARS, USDA—Cooperative States Res. Service (Grant no. 86-CSRS-2-2962) and the Utah Agric. Exp. Stn., Logan, UT 84322-4810. Journal Paper no. 4120.

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