Transport of root-respired CO₂ via the transpiration stream affects aboveground carbon assimilation and CO₂ efflux in trees.
Upward transport of CO₂ via the transpiration stream from belowground to aboveground tissues occurs in tree stems. Despite potentially important implications for our understanding of plant physiology, the fate of internally transported CO₂ derived from autotrophic respiratory processes remains unclear. We infused a ¹³CO₂-labeled aqueous solution into the base of 7-yr-old field-grown eastern cottonwood (Populus deltoides) trees to investigate the effect of xylem-transported CO₂ derived from the root system on aboveground carbon assimilation and CO₂ efflux. The ¹³C label was transported internally and detected throughout the tree. Up to 17% of the infused label was assimilated, while the remainder diffused to the atmosphere via stem and branch efflux. The largest amount of assimilated ¹³C was found in branch woody tissues, while only a small quantity was assimilated in the foliage. Petioles were more highly enriched in ¹³C than other leaf tissues. Our results confirm a recycling pathway for respired CO₂ and indicate that internal transport of CO₂ from the root system may confound the interpretation of efflux-based estimates of woody tissue respiration and patterns of carbohydrate allocation.
Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000, Gent, Belgium.
Jasper
J
Bloemen
Warnell School of Forestry and Natural Resources, University of Georgia, 180 East Green St, Athens, GA, 30602-2152, USA.
Mary Anne
MA
McGuire
Department of Biology, Georgia Southern University, PO Box 8042, Statesboro, GA, 30460-8042, USA.
Doug P
DP
Aubrey
Warnell School of Forestry and Natural Resources, University of Georgia, 180 East Green St, Athens, GA, 30602-2152, USA.
Robert O
RO
Teskey
Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000, Gent, Belgium.
Kathy
K
Steppe
D000388:Air; D001692:Biological Transport; D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes; D019069:Cell Respiration; D007553:Isotope Labeling; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000378:metabolism*; D018547:Plant Stems / Q000378:metabolism; D018526:Plant Transpiration / Q000502:physiology*; D014197:Trees / Q000033:anatomy & histology / Q000378:metabolism*
D002247:Carbon Isotopes; D002245:Carbon Dioxide; D002244:Carbon