Table 4.
Mean values for the photosynthetic parameters analyzed at PPFD = 1500 μmol photons m−2 s−1, Tleaf = 25 °C and VPD = 1.25 kPa. Data are mean ± SE. Different letters indicate statistically significant differences (P < 0.05) between Q. robur and Q. faginea. AN, net photosynthesis; gs, stomatal conductance; E, transpiration; iWUE = AN/gS, intrinsic water use efficiency; WUE = AN/E, instantaneous water use efficiency; gm, mesophyll conductance to CO2; Ci, substomatal CO2 concentration; Cc, chloroplastic CO2 concentration; Vc,max and Jmax, maximum velocity of carboxylation and maximum capacity for electron transport; Jflu, electron transport rate estimated by chlorophyll fluorescence.
| Q. robur | Q. faginea | |
|---|---|---|
| AN (µmol CO2 m−2 s−1) | 12.9 ± 0.5a | 19.6 ± 1.1b |
| gs (mol H2O m−2 s−1) | 0.252 ± 0.013a | 0.652 ± 0.078b |
| E (mol H2O m−2 s−1) | 2.5 ± 0.02a | 6.5 ± 0.8b |
| iWUE (μmol mol−1) | 51.2 ± 1.8a | 31.7 ± 3.1b |
| WUE (μmol mol−1) | 5.1 ± 0.3a | 3.0 ± 0.2b |
| gm (mol H2O m−2 s−1) | 0.060 ± 0.005a | 0.098 ± 0.07b |
| Ci (µmmol CO2 mol−1 air) | 288 ± 7a | 293 ± 4a |
| Cc (µmmol CO2 mol−1 air) | 80 ± 2a | 95 ± 4b |
| Vc,max (µmol m−2 s−1) | 206 ± 6a | 250 ± 4b |
| Jmax (µmol m−2 s−1) | 248 ± 10a | 292 ± 14b |
| Jflu (µmol m−2 s−1) | 266 ± 8a | 306 ± 13b |
| Jmax : Vc,max | 1.21 ± 0.03a | 1.19 ± 0.04a |