Photosynthetic performance of submerged macrophytes from lowland stream and lake habitats with contrasting CO2 availability

• Published in: The New phytologist Vol. 198; no. 4; pp. 1135 - 1142
• Main Authors: Baattrup‐Pedersen, Annette, Madsen, Tom Vindbæk, Riis, Tenna, Cavalli, Giulia
• Format: Journal Article
• Language: English
• Published: England New Phytologist Trust 01.06.2013; Wiley Subscription Services, Inc
• Subjects: acclimation; Alkalies; Alkalinity; Aquatic environment; Aquatic habitats; aquatic plant; Aquatic plants; Availability; Capacity; carbon; Carbon - metabolism; Carbon dioxide; Carbon Dioxide - pharmacology; Ecosystem; Freshwater; Hydrogen-Ion Concentration - drug effects; Lakes; lowland; Lowlands; Macrophytes; Nitrogen; Nitrogen - metabolism; nitrogen content; nutrient use efficiency; Photosynthesis; Photosynthesis - drug effects; photosynthetic nitrogen‐use efficiency (PNUE); Plant extracts; Plant growth; Plants; Plants - drug effects; Rivers; selection pressure; Stream habitats; Streams; Submerged plants; Tissue; tissue‐N
• ISSN: 0028-646X; 1469-8137; 1469-8137
• DOI: 10.1111/nph.12203

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.