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Elevated CO 2 stimulates associative N 2 fixation in a C 3 plant of the Chesapeake Bay wetland
Author(s) -
Dakora F. D.,
Drake B. G.
Publication year - 2000
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.2000.00610.x
Subject(s) - scirpus , photosynthesis , nitrogenase , biology , botany , spartina , zoology , carbon fixation , horticulture , nitrogen fixation , wetland , ecology , marsh , genetics , bacteria
In this study, the response of N 2 fixation to elevated CO 2 was measured in Scirpus olneyi , a C 3 sedge, and Spartina patens , a C 4 grass, using acetylene reduction assay and 15 N 2 gas feeding. Field plants grown in PVC tubes (25 cm long, 10 cm internal diameter) were used. Exposure to elevated CO 2 significantly ( P < 0·05) caused a 35% increase in nitrogenase activity and 73% increase in 15 N incorporated by Scirpus olneyi . In Spartina patens , elevated CO 2 (660 ± 1 μ mol mol − 1 ) increased nitrogenase activity and 15 N incorporation by 13 and 23%, respectively. Estimates showed that the rate of N 2 fixation in Scirpus olneyi under elevated CO 2 was 611 ± 75 ng 15 N fixed plant − 1 h − 1 compared with 367 ± 46 ng 15 N fixed plant − 1 h − 1 in ambient CO 2 plants. In Spartina patens , however, the rate of N 2 fixation was 12·5 ± 1·1 versus 9·8 ± 1·3 ng 15 N fixed plant − 1 h − 1 for elevated and ambient CO 2 , respectively. Heterotrophic non‐symbiotic N 2 fixation in plant‐free marsh sediment also increased significantly ( P < 0·05) with elevated CO 2 . The proportional increase in 15 N 2 fixation correlated with the relative stimulation of photosynthesis, in that N 2 fixation was high in the C 3 plant in which photosynthesis was also high, and lower in the C 4 plant in which photosynthesis was relatively less stimulated by growth in elevated CO 2 . These results are consistent with the hypothesis that carbon fixation in C 3 species, stimulated by rising CO 2 , is likely to provide additional carbon to endophytic and below‐ground microbial processes.