Table 1.
Effect of low air CO2 concentration around leaves on gas exchange and leaf hydraulics of water-stressed [foliar transpiration (E) <3 mmol m–2 s–1] hybrid poplar clones contrasting in drought tolerance
| Clone (drought tolerance) | C a | A Ci=275 (μmol m–2 s–1)a | g m_Ci=275 (mol m–2 s–1) | g sw (mol m–2 s–1) | E (mmol m–2 s–1) | K leaf (mmol m–2 s–1 MPa–1) | Ψleaf (MPa) |
|---|---|---|---|---|---|---|---|
| Okanese | Ambient | 18.7 (2.4)b | 0.224 (0.042) | 0.115 (0.053) | 1.65 (0.63) | 6.43 (2.1) | –0.87 (0.07) |
| (tolerant) | Low | 20.9 (2.4) | 0.270 (0.036) | 0.325 (0.053) | 4.08 (0.63) | 9.28 (2.0) | –0.97 (0.07) |
| Assiniboine | Ambient | 21.7 (2.3) | 0.285 (0.037) | 0.119 (0.051) | 1.64 (0.59) | 12.2 (2.2) | –0.76 (0.07) |
| (sensitive) | Low | 15.0 (2.6) | 0.204 (0.040) | 0.206 (0.058) | 3.07 (0.68) | 14.5 (2.9) | –1.06 (0.08) |
| P-valuesc | Clone | 0.69 | 0.96 | 0.22 | 0.34 | 0.04 | 0.66 |
| C a | 0.35 | 0.59 | 0.007 | 0.007 | 0.21 | 0.01 | |
| Clone×C a | 0.06 | 0.10 | 0.23 | 0.44 | 0.90 | 0.21 |
a Photosynthesis (A Ci=275) and mesophyll conductance (g m_Ci=275) measured at a normalized C i of 275 μmol mol–1, stomatal conductance to water (g sw), transpiration (E), leaf hydraulic conductance (K leaf), and leaf water potential (Ψleaf).
b Standard error in parentheses.
c Numerator d.f. = 1; denominator d.f. = 20 (A Ci=275, g sw, Ψleaf, E), 17 (g m_Ci=275), 11 (K leaf).