title: Photosynthetic performance of submerged macrophytes from lowland stream and lake habitats with contrasting CO₂ availability.
abstract: · We examine the photosynthetic response of submerged plants from streams and lakes with contrasting free-CO₂ and nitrogen (N) availability. We hypothesized that: the photosynthetic capacity of stream plants is higher because of higher N availability; the photosynthetic N-use efficiency (PNUE) is also higher because stream plants are acclimated to higher free-CO₂; and PNUE is lower in aquatic compared to terrestrial plants. · We tested these hypotheses by measuring tissue-N, photosynthetic capacity and inorganic C extraction capacity in plants collected from streams and lakes and by comparing the PNUE of aquatic plants with previously published PNUE of terrestrial plants. · We found that the organic N content was consistently higher in stream (3.8-6.3% w/w) than in lake plants (1.2-4.3% w/w). The photosynthetic capacity correlated positively with tissue-N. The relationships were similar for stream and lake plants, indicating that N allocation patterns were similar despite variability in free-CO₂ between the two habitats. · The slope of the relationship between photosynthetic capacity and tissue-N was lower than found for terrestrial plants, whereas the compensatory N content for photosynthesis was similar. This suggests that PNUE is lower in aquatic plants, perhaps reflecting that the selection pressure for a high C fixation rate per unit N is reduced as a result of low inorganic C availability in the aquatic environment.
authors.affiliation: Department of Bioscience, Aarhus University, Silkeborg, Denmark.
authors.forename: Annette
authors.initials: A
authors.lastname: Baattrup-Pedersen
authors.affiliation: Department of Bioscience, Aarhus University, Århus, Denmark.
authors.forename: Tom Vindbaek
authors.initials: TV
authors.lastname: Madsen
authors.affiliation: Department of Bioscience, Aarhus University, Århus, Denmark.
authors.forename: Tenna
authors.initials: T
authors.lastname: Riis
authors.affiliation: Department of Bioscience, Aarhus University, Silkeborg, Denmark.|Department of Bioscience, Aarhus University, Århus, Denmark.
authors.forename: Giulia
authors.initials: G
authors.lastname: Cavalli
mesh_terms: D000468:Alkalies; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000494:pharmacology*; D017753:Ecosystem; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D060106:Lakes; D009584:Nitrogen / Q000378:metabolism; D010788:Photosynthesis / Q000187:drug effects*; D010944:Plants / Q000187:drug effects*; D045483:Rivers
chemical_list: D000468:Alkalies; D002245:Carbon Dioxide; D002244:Carbon; D009584:Nitrogen