Table 4. The parameters (± S.E.) of the C-specific light-response curves for gross and net photosynthetic O2 evolution of T. erythraeum IMS101 (n = 3).
| Parameters | Units | N2 | NH4+ | NO3- |
|---|---|---|---|---|
| Gross O2 evolution | ||||
| E0mC | mmol O2 (g C)-1 h-1 | 6.05 (0.37)[A] | 14.71 (1.20)[C] | 10.98 (0.33)[B] |
| Ek | μmol photons m-2 s-1 | 238 (55) | 227 (44) | 255 (55) |
| αgC | μmol O2 (g C)-1 h-1 (μmol photons m-2 s-1)-1 | 27.9 (5.3)[A] | 67.7 (8.2)[B] | 49.8 (15.1) |
| ɸmgross | mol O2 (mol photons)-1 | 0.07 (0.01)[A] | 0.12 (0.01)[B] | 0.09 (0.03) |
| E0:Nfix | mol O2 (mol N2)-1 | 31 (4)[A] | 289 (32)[B] | 185 (57)[B] |
| Net Photosynthesis | ||||
| PnetmC | mmol O2 (g C)-1 h-1 | 3.75 (0.27)[A] | 11.48 (1.56)[B] | 9.59 (0.37)[B] |
| Ek | μmol photons m-2 s-1 | 250 (69) | 277 (8) | 220 (37) |
| αnC | μmol O2 (g C)-1 h-1 (μmol photons m-2 s-1)-1 | 16.8 (3.4)[A] | 41.5 (5.8)[B] | 46.1 (8.0)[B] |
| RdC | mmol O2 (g C)-1 h-1 | -1.63 (0.19) | -1.53 (0.28) | -1.16 (0.76) |
| ɸmnet | mol O2 (mol photons)-1 | 0.04 (0.01)[A] | 0.08 (0.02)[B] | 0.09 (0.01)[B] |
| Pnet:Nfix | mol O2 (mol N2)-1 | 18 (1)[A] | 207 (29)[B] | 163 (36)[B] |
| Gross (x) vs. Net (y) | ||||
| slope | Dimensionless | 0.60 (0.02)[A] | 0.82 (0.03)[B] | 0.83 (0.01)[B] |
Abbreviations; E0mC, the C-specific maximum gross O2 evolution rate; PnetmC, the C-specific maximum net O2 evolution rate; Ek, the light saturation parameter; αgC and αnC are the C-specific initial slopes the light response curve for net and gross photosynthesis; ɸmgross and ɸmnet are the maximum quantum efficiencies of gross and net O2 evolution; RdC, the C-specific dark respiration rate; slope, the gradient of the regression between PnetC and E0C; E0:Nfix and Pnet:Nfix, the ratio of gross and net photosynthesis to N2 fixation, where rates of E0 and Pnet were calculated at 400 μmol photons m-2 s-1, matching to light intensity of the N2 fixation incubations; slope, the gradient of the regression between PnetC and E0C. The r2 values of all curve fits were > 0.982. Letters in parenthesis indicate significant differences between CO2 treatments (One Way ANOVA, Tukey post hoc test; P < .05); where [B] is significantly greater than [A] and [C] is significantly greater than [B] and [A].