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This article in AJ

  1. Vol. 81 No. 4, p. 692-695
    Received: Aug 15, 1988

    * Corresponding author(s):


Elongation and Branching of Roots on Soybean Plants in a Carbon Dioxide-Enriched Aerial Environment

  1. D. Del Castillo,
  2. B. Acock ,
  3. V. R. Reddy and
  4. M. C. Acock
  1. D ep. of Soil Sci., North Carolina State Univ., Raleigh, NC 27695;
    U SDA/ARS/NRI Systems Res. Lab., Beltsville, MD 20705
    C rop Simulation Res. Unit, Mississippi State, MS 39762.



Plants grown in high CO2 concentrations ([CO2]) often have a higher root weight than those grown in low [CO2]. It is usually assumed that the plants with this extra root weight can explore a greater volume of soil and will, therefore, have more water available to them. To test this assumption, soybean [Glycine max (L.) Merr. cv. Forrest] plants were grown in outdoor, sunlit plant-growth chambers in [CO2] of 330, 450, 600, and 800 μL L−1 throughout the growing season. The soil containers in the growth chambers had a glass side and new root growth appearing at the glass was measured and marked two or three times each week. Root weight at the end of the season (93 d after emergence) was 26 to 31% higher in [C02]-enriched chambers compared with the 330 μL L−1 treatment, and cumulative root length was approximately proportional to [CO2]. However, CO2 treatment did not affect the rate of elongation of individual root axes. Instead, there was a significant linear increase in the number of actively growing roots with increased [CO2]. Plants grown in 800 μL L−1 had 65% more actively growing roots than plants grown in 330 μL L−1. Thus, growing a plant in high [CO2] enabled it to explore a given volume of soil more thoroughly, but did not increase the volume of soil explored.

Contribution from Mississippi Agric. and For. Exp. Stn., Dep. of Agronomy, Mississippi State Univ., and USDA/ARS/NRI Systems, Res Lab. Supported in part by the U.S. Dep. of Energy, Carbon Dioxide Res. Div., Interagency Agreement No. DE-AIO1-81ER-60001.

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