title: Photosynthetic CO2 uptake in seedlings of two tropical tree species exposed to oscillating elevated concentrations of CO2.
abstract: Do short-term fluctuations in CO2 concentrations at elevated CO2 levels affect net CO2 uptake rates of plants? When exposed to 600 microl CO2 l(-1), net CO2 uptake rates in shoots or leaves of seedlings of two tropical C3 tree species, teak (Tectona grandis L. f.) and barrigon [Pseudobombax septenatum (Jacq.) Dug.], increased by 28 and 52% respectively. In the presence of oscillations with half-cycles of 20 s, amplitude of ca. 170 microl CO2 l(-1) and mean of 600 microl CO2 l(-1), the stimulation in net CO2 uptake by the two species was reduced to 19 and 36%, respectively, i.e. the CO2 stimulation in photosynthesis associated with a change in exposure from 370 to 600 microl CO2 l(-1) was reduced by a third in both species. Similar reductions in CO2-stimulated net CO2 uptake were observed in T. grandis exposed to 40-s oscillations. Rates of CO2 efflux in the dark by whole shoots of T. grandis decreased by 4.8% upon exposure of plants grown at 370 microl CO2 l(-1) to 600 microl CO2 l(-1). The potential implications of the observations on CO2 oscillations and dark respiration are discussed in the context of free-air CO2 enrichment (FACE) systems in which short-term fluctuations of CO2 concentration are a common feature.
authors.affiliation: Smithsonian Tropical Research Institute, P.O. Box 2072, Balboa, Ancon, Republic of Panama.
authors.forename: Joseph A M
authors.initials: JA
authors.lastname: Holtum
authors.forename: Klaus
authors.initials: K
authors.lastname: Winter
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D019686:Lamiaceae / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D019660:Malvaceae / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D009991:Oscillometry; D010788:Photosynthesis; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D014197:Trees / Q000378:metabolism*; D014329:Tropical Climate
chemical_list: D002245:Carbon Dioxide