Skip to main content
. 2015 Oct 3;7:plv116. doi: 10.1093/aobpla/plv116

Table A2.

Symbols, values and units of different parameters, variables and constants used in the photosynthetic and stomatal conductance models. 1Values taken from Schultz (2003). 2Values taken from Harley et al. (1992). 3Constant used for measurement in the leaf chamber of the LcPro (ADC Lcpro, BioScientific Ltd, Hoddesdon, Hertfordshire, UK).

Symbol Value Unit Description
Photosynthesis model
α 0.201 µmol CO2 µmol photon−1 Photochemical efficiency or initial quantum yield
 Γ* Pa Compensation point for CO2 in the absence of mitochondrial respiration
A µmol CO2 m−2 s−1 Net photosynthetic rate
Ac µmol CO2 m−2 s−1 RUBISCO-limited photosynthetic rate
Aj µmol CO2 m−2 s−1 Electron transport rate-limited photosynthetic rate
Ap µmol CO2 m−2 s−1 Triose phosphate utilization-limited photosynthetic rate
 c Scaling constant
Ca Pa Ambient CO2 partial pressure
Ci Pa Intercellular CO2 partial pressure
 ΔHa kJ mol−1 Enthalpy of activation
 ΔHd 2002 kJ mol−1 Enthalpy of deactivation
Kc Pa Michaelis–Menten constant of RUBISCO for CO2
Ko kPa Michaelis–Menten constant of RUBISCO for O2
J µmol electron m−2 s−1 Electron transport rate
Jmax µmol m−2 s−1 Maximum electron transport rate
 Na g m−2 Area based N content
 Namin g m−2 Minimum value of Na at which P25 → 0
O 21 kPa Oxygen partial pressure
P25 µmol m−2 s−1 Value of Vcmax, Jmax, TPU or Rd at 25 °C
 PPFD µmol m−2 s−1 Photosynthetic photon flux density
R 0.00831 kJ mol−1 K−1 Universal gas constant for perfect gases
Rd µmol m−2 s−1 Mitochondrial respiration in light
 ΔS 0.6352 kJ mol−1 Entropy term
SNa µmol g−1 s−1 Slope of the relationship between Na and Vcmax, Jmax, TPU or Rd
Tleaf °C Leaf temperature in degrees Celsius
Tk Kelvin degrees Leaf temperature in Kelvin
 TPU µmol m−2 s−1 Triose phosphate utilization rate
Vc µmol m−2 s−1 Carboxylation rate
Vo µmol m−2 s−1 Oxygenation rate
Vcmax µmol m−2 s−1 Maximum rate of RUBISCO carboxylation
Stomatal conductance model
Cs Pa CO2 partial pressure at the leaf surface
gb 2.3573 mol m−2 s−1 Boundary layer conductance
gs mmol m−2 s−1 Stomatal conductance
go 0.020 mmol m−2 s−1 Residual stomatal conductance when A → 0
 VPD kPa Water VPD
Do 2.86 kPa Empirical factor assessing stomata sensitivity to VPD
a1 12.5 Empirical stomatal conductance factor