Defined variables

This table shows variable names and units that should be used in data tables. Expected range values cover most plants for standard experimental conditions and may be used as a guide for quality checking.

variableName	variableUnit	variableDescription	expectedValueRangeMin	expectedValueRangeMax
Instrument outputs
date	YYYY-MM-DD	Date of observation
time	HH:MM:SS	Time of observation
record	-	Observation record number
area	cm²	Leaf area
A	µmol m⁻² s⁻¹	Net CO₂ exchange per leaf area	-20	120
Amax	µmol m⁻² s⁻¹	Highest rate of light and CO₂ saturated A	-20	120
Asat	µmol m⁻² s⁻¹	Highest rate of light saturated A at ambient CO₂ concentration	-20	120
Ci	µmol mol⁻¹	Intercellular CO₂ concentration in air	0	5000
CO2r	µmol mol⁻¹	CO₂ concentration in wet air entering chamber	0	5000
CO2s	µmol mol⁻¹	CO₂ concentration in wet air inside chamber	0	5000
dCO2	µmol mol⁻¹	Sample minus reference CO₂ concentration in air
dH2O	mmol mol⁻¹	Sample minus reference H₂O concentration in air
E	mmol m⁻² s⁻¹	Transpiration rate of H₂O per leaf area. Note that output units from some instruments are in mol and will require conversion.
flow	µmol s⁻¹	Flow rate of air into chamber
gbw	mmol m⁻² s⁻¹	Boundary layer conductance to water vapor per leaf area
gsw	mmol m⁻² s⁻¹	Stomatal conductance to water vapor per leaf area	0	1000
H2Or	mmol mol⁻¹	H₂O concentration in air entering chamber
H2Os	mmol mol⁻¹	H₂O concentration in air inside chamber
Patm	kPa	Atmospheric pressure	50	120
Qin	µmol m⁻² s⁻¹	In-chamber photosynthetic flux density (PPFD) incident on the leaf, quanta per area	0	5000
Qout	µmol m⁻² s⁻¹	External photosynthetic flux density (PPFD), quanta per area	0	5000
RHr	%	Relative humidity of air entering the chamber	0	100
RHs	%	Relative humidity of air inside the chamber	0	100
Tair	°C	Air temperature inside the chamber	-20	70
Tleaf	°C	Leaf surface temperature	-20	70
VPDleaf	kPa	Leaf to air vapor pressure deficit	0	5
Calculated parameters
AsatG	µmol m⁻² s⁻¹	Maximum rate of gross CO₂ assimilation derived from the light response curve. Equivalent to total of CO₂ assimilation and CO₂ release.
CE	mol m⁻² s⁻¹	Maximum carboxylation efficiency, based on an empirical determination of the initial slope of an ACi curve
CiCa	-	Ratio of intercellular CO₂ to sample chamber CO₂
CO2comp	µmol mol⁻¹	CO₂ compensation point
gm	mol m⁻² s⁻¹	Mesophyll conductance to CO₂ per leaf area
J	µmol m⁻² s⁻¹	Rate of electron transport per leaf area at measurement temperature calculated assuming infinite mesophyll conductance for a given irradiance e.g. J1800. Or at reference temperature e.g., J1800,25	0	600
Jmax	µmol m⁻² s⁻¹	Maximum rate of electron transport per leaf area at measurement temperature calculated assuming infinite mesophyll conductance and saturating light	0	600
Jmax25	µmol m⁻² s⁻¹	Maximum rate of electron transport per leaf area, at the reference temperature 25°C calculated assuming infinite mesophyll conductance and saturating light	0	600
LCP	µmol m⁻² s⁻¹	Light compensation point. The lowest photosynthetic photon flux density at which positive net CO₂ assimilation is observed
LSP	µmol m⁻² s⁻¹	Light saturation point. The irradiance at which further increases in irradiance level do not increase net CO₂ assimilation rate.
PhiCO2a	mol mol⁻¹	Maximum quantum yield of CO₂ assimilation based on absorbed irradiance
PhiCO2i	mol mol⁻¹	Maximum quantum yield of CO₂ assimilation based on incident irradiance
PhiJa	mol mol⁻¹	Maximum quantum yield of electron transport based on arbsorbed irradiance
PhiJi	mol mol⁻¹	Maximum quantum yield of electron transport based on incident irradiance
Rdark	µmol m⁻² s⁻¹	CO₂ release from the leaf in the dark, at measurement temperature, reported as a positive value
Rdark25	µmol m⁻² s⁻¹	CO₂ release from the leaf in the dark, at the reference temperature of 25°C, reported as a positive value
Rday	µmol m⁻² s⁻¹	CO₂ release from the leaf in the light, reported as a positive value
Rday25	µmol m⁻² s⁻¹	CO₂ release from the leaf in the light, at the reference temperature of 25°C, reported as a positive value.
Theta	-	Empirical convexity parameter derived from the non-rectangular hyperbolic model of the light response curve
TPU	µmol m⁻² s⁻¹	Triose phosphate utilization rate per leaf area at measurement temperature
TPU25	µmol m⁻² s⁻¹	Triose phosphate utilization rate per leaf area at the reference temperature 25°C
Vcmax	µmol m⁻² s⁻¹	Maximum rate of carboxylation at measurement temperature, calculated assuming infinite mesophyll conductance, i.e. apparent Vcmax	0	500
Vcmax25	µmol m⁻² s⁻¹	Maximum rate of carboxylation, at the reference temperature 25°C, calculated assuming infinite mesophyl conductance, i.e. apparent Vcmax	0	500
Vpmax	µmol m⁻² s⁻¹	Phosphoenolpyruvate (PEP) saturated PEP carboxylation at measurement temperature
WUEi	µmol mol⁻¹	Intrinsic water use efficiency. Net CO₂ exchange per leaf area divided by stomatal conductance to water vapor per leaf area
Constants
Alpha	-	Leaf absorptance of visible radiation (400-730 nm)	0	1
EaGammaStar	kJ mol⁻¹	Activation energy associated with the temperature response of gammaStar
EaKc	kJ mol⁻¹	Activation energy associated with the temperature response of Kc
EaKo	kJ mol⁻¹	Activation energy associated with the temperature response of Ko
EaVcmax	kJ mol⁻¹	Activation energy associated with the temperature response of Vcmax
EaVomax	kJ mol⁻¹	Activation energy associated with the temperature response of Vomax, the maximum rate of oxygenation
f	-	Fraction of light absorbed by photosystem II that is not used for photochemistry
gammaStar25	µmol mol⁻¹	CO₂ compensation point in the absence of non-photorespiratory CO₂ release at the reference temperature of 25°C
Kc25	µmol mol⁻¹	Michaelis constant for CO₂ concentration in air at the reference temperature of 25°C
Ko25	mmol mol⁻¹	Michaelis constant for O₂ concentration in air at the reference temperature of 25°C
Oi	mmol mol⁻¹	Intercellular O₂ concentration in air (default 210 unless experimentally manipulated)
Tau25	-	CO₂:O₂ specificity ratio at a reference temperature of 25°C
TauQ10	-	Q10 temperature response parameter used to scale Tau25