title: Land plants of amphibious Littorella uniflora (L.) Aschers. maintain utilization of CO2from the sediment.
abstract: Submerged macrophytes of the isoetid life form derive the majority of their CO2for photosynthesis from the sediment. The experiments described here were designed to test the hypothesis that root uptake of CO2is important also in the terrestrial form of Littorella uniflora. The results of14CO2experiments showed that sediment CO2contributed 56% of the total fixation at 0.1MM CO2in the rhizosphere, 83% at 0.5MM and 96% at 2.5MM. Sediment CO2in emergent Littorella stands ranged from 0.1 to 1.0MM and averaged 0.5MM. Measurements of the net CO2exchange over the leaves showed an even higher dependence of the sediment as CO2source. Littorella leaves had no stomata at the base and densities (ca. 100 mm-2) typical of terrestrial plants at the tip, allowing sediment-derived CO2to be supplied along the length of the leaf. The stomata permit supply of CO2from the air during periods of reduced sediment CO2concentrations (e.g. if the sediment dries up) and regulate transpiration.
authors.affiliation: Freshwater Biological Laboratory, University of Copenhagen, 51 Helsingørsgade, DK-3400, Hillerød, Denmark.
authors.forename: Soren Laurentius
authors.initials: SL
authors.lastname: Nielsen
authors.affiliation: Department of Ecology, University of Barcelona, 645 Av. Diagonal, 08028, Barcelona, Spain.
authors.forename: Esperança
authors.initials: E
authors.lastname: Gacia
authors.affiliation: Freshwater Biological Laboratory, University of Copenhagen, 51 Helsingørsgade, DK-3400, Hillerød, Denmark.
authors.forename: Kaj
authors.initials: K
authors.lastname: Sand-Jensen
keywords: Carbon uptake; Littorella uniflora; Sediment CO2 utilization; Terrestrial isoetids