Carbon dioxide transport inxylem causes errors in estimation of rates of respiration in stemsand branches of trees |
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Authors: | R. O. Teskey,& M. A. Mcguire |
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Affiliation: | School of Forest Resources,University of Georgia, Athens, GA 30602, USA |
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Abstract: | Complementary laboratory and field experiments showed that theinternal transport of carbon dioxide (CO2) in the xylemof trees is an important pathway for carbon movement. Carbon dioxidereleased by respiration dissolves in sap and moves upward in thetranspirational stream. The concentration of CO2 in xylemsap can be up to three orders of magnitude greater than that foundin the atmosphere. In the present experiments, diffusion outwardof a portion of xylem‐transported CO2 caused a substantialoverestimation of the apparent rate of stem and branch respiration.Rates of CO2 efflux were linearly related to sap CO2 concentration.Direct manipulations of xylem sap CO2 concentration producedrapid and reversible changes in CO2 efflux from stemsand branches, in some cases quadrupling the rate of efflux. Theseresults demonstrated that apparent rates of stem and branch respirationof trees are in large part a by‐product of the rate of CO2 diffusionfrom xylem sap. |
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Keywords: | Liriodendron tulipifera Quercus alba Pinus taeda CO2 microelectrodes sap velocity total dissolved carbon xylem sap CO2 concentration |
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