Conductance to CO2 (umol / (m^2 s Pa))
- g_tc: total conductance to CO2
- g_uc: cuticular conductance to CO2
- g_bc: boundary layer conductance to CO2
- g_mc: mesophyll conductance to CO2
- g_sc: stomatal conductance to CO2
.get_gtc(pars, unitless).get_guc(pars, surface, unitless)
.get_gbc(pars, surface, unitless)
.get_gmc(pars, surface, unitless)
.get_gsc(pars, surface, unitless)
Concatenated parameters (leaf_par, enviro_par, and constants)
Logical. Should units be set? The function is faster when FALSE, but input must be in correct units or else results will be incorrect without any warning.
Leaf surface (lower or upper)
Total conductance to CO2 is the sum of parallel conductances on the lower (\(g_\mathrm{c,lower}\)) and upper (\(g_\mathrm{c,upper}\)) leaf portions:
$$g_\mathrm{c,total} = g_\mathrm{c,lower} + g_\mathrm{c,upper}$$
Each partial conductance consists of two parallel conductances, the cuticular conductance (\(g_\mathrm{u,c}\)) and the in-series conductances through mesophyll (\(g_\mathrm{m,c}\)), stomata (\(g_\mathrm{s,c}\)), and boundary layer (\(g_\mathrm{b,c}\)). To simplify the formula, I use substitute resistance where \(r_x = 1 / g_x\). For surface \(i\):
$$g_{\mathrm{c},i} = g_{\mathrm{u},i} + (1 / (r_{\mathrm{m},i} + r_{\mathrm{s},i} + r_{\mathrm{b},i}))$$
The cuticular, stomatal, and mesophyll conductances can be the same or different for upper and lower. The partitioning factors (\(k_x\)) divide the conductance between surfaces while keeping the total conductance constant:
$$g_{x,\mathrm{lower}} = g_x (1 / (1 + k_x))$$ $$g_{x,\mathrm{upper}} = g_x (k_x / (1 + k_x))$$ $$g_x = g_{x,\mathrm{lower}} + g_{x,\mathrm{upper}}$$
How the partitioning factors work:
| \(k_x\) | description |
| 0 | all conductance on lower surface/portion |
| 0.5 | 2/3 conductance on lower surface |
| 1 | conductance evenly divided between surfaces/portions |
| 2 | 2/3 conductance on upper surface |
The boundary layer conductances for each are calculated on the basis of mass and heat transfer (see .get_gbc).
| Symbol | R | Description | Units | Default |
| \(g_\mathrm{mc}\) | g_mc |
mesophyll conductance to CO2 (T_leaf) | \(\mu\)mol CO2 / (m\(^2\) s Pa) | calculated |
| \(g_\mathrm{sc}\) | g_sc |
stomatal conductance to CO2 | \(\mu\)mol CO2 / (m\(^2\) s Pa) | 4 |
| \(g_\mathrm{uc}\) | g_uc |
cuticular conductance to CO2 | \(\mu\)mol CO2 / (m\(^2\) s Pa) | 0.1 |
| \(k_\mathrm{mc}\) | k_mc |
partition of \(g_\mathrm{mc}\) to lower mesophyll | none | 1 |
| \(k_\mathrm{sc}\) | k_sc |
partition of \(g_\mathrm{sc}\) to lower surface | none | 1 |
| \(k_\mathrm{uc}\) | k_uc |
partition of \(g_\mathrm{uc}\) to lower surface | none | 1 |