Table 2.

CO₂ transfer conductances across the intercellular air space (g_ias, m s⁻¹), the liquid phase (g_liq, m s⁻¹) and the mesophyll conductance for CO₂ (g_m, mol m⁻² s⁻¹) calculated from anatomical measurements in A. pinsapo and A. alba needles grown in the open field (OI) and in the understory (UI). Data are mean ± SE (n = 6). Different letters indicate statistically significant differences (P < 0.05) between OI and UI within the same species.

	A. pinsapo OI	A. pinsapo UI	A. alba OI	A. alba UI
gias (m s−1)	0.0074 ± 0.0004 a	0.0153 ± 0.0011 b	0.0179 ± 0.0013 a	0.0212 ± 0.0016 a
gliq (m s−1)	0.0053 ± 0.0005 a	0.0022 ± 0.0003 b	0.0021 ± 0.0002 a	0.0020 ± 0.0002 a
gm (mol m−2 s−1)	0.117 ± 0.016 a	0.077 ± 0.010 b	0.074 ± 0.012 a	0.072 ± 0.010 a