Holtum, Joseph A.M., and Winter, Klaus (2003) Photosynthetic CO2 uptake in seedlings of two tropical tree species exposed to oscillating elevated concentrations of CO2. Planta, 218 (1). pp. 152-158.

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Abstract

Do short-term fluctuations in CO2 concentrations at elevated CO2 levels affect net CO2 uptake rates of plants? When exposed to 600 µl 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 µl CO2 l–1 and mean of 600 µl 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 µl 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 µl CO2 l–1 to 600 µl 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.

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