Table I. List of symbols with description and units.

Symbol	Description	Units
A	Net CO2 assimilation rate	μmol m−2 s−1
Ac	RuBP carboxylation-limited CO2 assimilation rate	μmol m−2 s−1
Aj	RuBP regeneration-limited CO2 assimilation rate	μmol m−2 s−1
A/E	Water-use efficiency	mmol CO2 mol−1 water
ca	CO2 concentration of the atmosphere	μmol mol−1
ci/ca	Ratio of intercellular to atmospheric CO2 concentration	Dimensionless
ci	Leaf intercellular CO2 concentration	μmol mol−1
cs	CO2 concentration at the leaf surface	μmol mol−1
D	Stomatal density	mm−2
Ds	Leaf-to-air vapor pressure difference at the leaf surface	kPa
D0	Fitted parameter in Equation 2	kPa
E	Transpiration rate	mol m−2 s−1
gbc	Leaf boundary layer conductance to CO2	mol m−2 s−1
gc	Stomatal conductance to CO2	mol m−2 s−1
gc(max)	Maximum stomatal conductance to CO2	mol m−2 s−1
gw	Stomatal conductance to water vapor	mol m−2 s−1
gw(max)	Maximum stomatal conductance to water vapor	mol m−2 s−1
g0	Intercept in Equations 1, 2, and 3, representing minimum gw	mol m−2 s−1
g1	Slope in Equation 1 (a fitted parameter)	Dimensionless
g1M	Fitted parameter in Equation 3	(kPa)0.5
H	Relative humidity at the leaf surface (as a fraction)	Dimensionless
Jmax	Maximum potential electron transport rate	μmol m−2 s−1
Rd	Leaf respiration rate	μmol m−2 s−1
S	Stomatal size	μm2
Vcmax	Maximum RuBP carboxylation rate	μmol m−2 s−1
∂A/∂gw	Sensitivity of A to gw	mmol mol−1
∂E/∂gw	Sensitivity of E to gw	mmol mol−1
∂E/∂A	Sensitivity of E to A, or gain ratio	mmol water μmol−1 CO2
Γ	CO2 compensation point including respiration	μmol mol−1
Γ*	CO2 compensation point without dark respiration	μmol mol−1
λ	Marginal water cost of leaf carbon	mmol water μmol−1 CO2