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Crop Science Abstract -

Recovery of Photosynthesis after Environmental Stress in Soybean Grown under Elevated CO2


This article in CS

  1. Vol. 38 No. 4, p. 948-955
    Received: Aug 11, 1997

    * Corresponding author(s): r.ferris@reading.ac.uk
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  1. Rachel Ferris ,
  2. T. R. Wheeler,
  3. P. Hadley and
  4. R. H. Ellis
  1. D ep. of Horticulture and Landscape, The Univ. of Reading, Plant Science Lab., Whiteknights, P.O. Box 221, Reading RG66AS, UK
    P lant Environment Lab., Dep. of Agriculture, Univ. of Reading, Cutbush Lane, Shinfield, Reading RG2 9AD, UK



Episodes of high temperature and water deficit may be more frequent under predicted future climates of warmer mean temperatures and elevated CO2. This study investigated whether the effects of an episode of high air temperature (HT, 43°C as a daily maximum), water deficit (WD), or both, had the same effect on the recovery photosynthesis and on leaf water relations of soybean [Glycine max (L.) Merr., cv. Fiskeby V] grown at ambient CO2 (aCO2) or elevated CO2 (eCO2). An 8-d period of HT, WD, or both (HTWD) were imposed during early seed filling of soybean grown in glasshouses at either 362 or 685 ;μmol mo1−1 CO2. Photosynthesis (Amax), stomatal conductance (g5), and water relations were measured in fully expanded upper-canopy leaves. Immediately after the 8-d treatments at 60 d after sowing (DAS), Amax was reduced by 31, 48, and 64% in aCO2 and by 28, 39, and 49% in eCO2 under HT, WD, and HTWD, respectively, but no significant interactions were detected. At 60 DAS, g5 was reduced by WD and HTWD in aCO2 but not by HT while there was little change in g5 by WD, HT, and HTWD under eCO2. Amax fully recovered under WD in eCO2 by 66 DAS, while Amax remained reduced under WD in aCO2. Under each CO2 concentration, almost full recovery of Amax occurred under HT by 75 DAS but under HTWD Amax never attained control values. At 60 DAS, early morning leaf water potential (ψ) was lower after HT, WD, and HTWD and Amax was a negative function of ψ, at each CO2 concentration. The results suggest that full recovery of Amax from WD was only possible under eCO2, because at aCO2, immediately after the stress episode, ψ was below the threshold for chloroplast damage.

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