Elongation and branching of roots on soybean plants in a carbon dioxide-enriched aerial environment
1989
Del Castillo, D. | Acock, B. | Reddy, V.R. | Acock, M.C.
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 microliter 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 [CO2]-enriched chambers compared with the 330 microliter 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 microliter L-1 had 65% more actively growing roots than plants grown in 330 microliter 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.
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