Table II.

The breakdown of total leaf CO₂ conductance (g_leaf) into its components, stomatal (g_s) (from gas exchange) and internal (g_i) (from Δ¹³C, plus error from 95% confidence limits of the slopes)

Species	gleaf
		gs	gi
				gw	gch	gch/gw	CAleaf
Tobacco	0.155	0.224	0.50 (0.12)	1.12 (0.33)	0.90	0.8	623
Soy	0.141	0.253	0.32 (0.05)	1.31 (0.45)	0.42	0.3	318
Oak	0.102	0.166	0.27 (0.09)	0.35 (0.04)	1.13	3.2	2,016a

With Δ¹⁸O, g_i is further partitioned into wall conductance to C_cs, g_w, and the residual conductance within the chloroplast, (g_ch). All units are mol CO₂ m⁻² s⁻¹. The ratio of chloroplast to wall conductance is also shown g_ch/g_w. Average CA_leaf activity is shown for comparison (μmol m⁻² s⁻¹).

^aIn the absence of direct CA measurements in the oak species used here, CA_leaf is estimated from the average CA activity observed other oak species (see text).