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 |