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This article in CS

  1. Vol. 24 No. 2, p. 361-366
    Received: Mar 7, 1983

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Influence of Elevated CO2 on Growth of Soybean Plants1

  1. Hugo H. Rogers,
  2. Jennifer D. Cure,
  3. Judith F. Thomas and
  4. Joy M. Smith2



Continuing use of fossil fuels in industrialized countries has created a need to understand growth responses of major crop species to elevated concentrations of CO2. An analysis was therefore undertaken of the growth of soybeans [Glycine max (L.) Merr. ‘Bragg’] grown in pots in open top field chambers at six CO2 concentrations ranging from 332 μL L-1 (ambient) to 910 μL L-1. Major growth response occurred with the first increments of added CO2 with a maximum 66% increase in total vegetative dry matter at the 910 μL L-1 CO2 level. Dry weight increases were proportionate among vegetative plant parts, although the harvest index was found to decrease slightly. Greater absolute growth rates in elevated CO2 treatments were associated with greater rates of branch and internode elongation, leaf initiation, and leaf expansion. Yield increases represented greater seed numbers per plant rather than larger seeds. Percentage protein of seed decreased with CO2 enrichment. In the interval from day 5 to 2 weeks after planting, mean relative growth rate (RGR) increased asymptotically with CO2 concentration. Of the two components of RGR, the mean net assimilation rate (NAR) increased dramatically and mean leaf area ratio (LAR) decreased. In the intervals from week 2 to 7 and from week 7 to 12, RGR became constant across CO2 treatments as the positive response of NAR and the negative response of LAR became less pronounced. Both RGR and NAR fell through the vegetative growth phase at each CO2 level. The adjustment in LAR resulted from a decrease in specific leaf area while leaf weight ratio remained unaffected by CO2.

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