Table I.
Symbols used in the text
| Symbol | Description |
|---|---|
| A | Net CO2 assimilation |
| a | Fractionation during diffusion of CO2 from the mesophyll to the atmosphere (7.7‰) |
| α | Fractionation factor for 18O between water and CO2 at 25°C (41.1‰) |
| Δea | 18O enrichment of CO2 at the site of exchange compared to the atmosphere when the CO2 is in full isotopic equilibrium with the water |
| Δca | 18O enrichment of CO2 at the site of exchange compared to the atmosphere |
| Δ13C | 13CO2 isotope discrimination |
| Δ18O | C18OO isotope discrimination |
| δ18O | Isotopic ratio of oxygen (‰ relative to VSMOW) |
| δa | 18O isotopic composition of water vapor in the air (‰ relative to VSMOW) |
| δc | The dilution corrected value of δ18O |
| δe | 18O isotopic composition of water at the site of evaporation in the leaf (‰ relative to VSMOW) |
| δex | 18O isotopic composition of water at the site of CO2-H2O oxygen exchange (‰ relative to VSMOW) |
| δg | δ18O value of the equilibrating CO2 |
| δm | Measured δ18O value |
| δt | 18O isotopic composition of water transpired by the leaf (‰ relative to VSMOW) |
 |
18O isotopic composition of water sample (‰ relative to VSMOW) |
 |
Dilution corrected 18O isotopic composition of the water sample |
 |
Dilution corrected 18O isotopic composition of reference water no. 1 |
 |
Dilution corrected 18O isotopic composition of reference water no. 2 |
 |
The 18O isotopic composition of reference water no. 1 relative to VSMOW (−6.44‰) |
 |
The 18O isotopic composition of reference water no. 2 relative to VSMOW (−22.83‰) |
| E | Transpiration rate |
| ea | Vapor pressure in the atmosphere |
| ei | Vapor pressure in the leaf intercellular air spaces |
| ɛ | pm/(pa − pm) |
| ɛk | Kinetic fractionation during diffusion of water from leaf intercellular air spaces to the atmosphere |
| ɛw | The equilibrium 18O fractionation between CO2 and water (40.17‰ at 30°C) |
| ɛ+ | The equilibrium 18O fractionation between liquid and vapor water (8.77‰ at 30°C) |
| Fin | Gross influx of CO2 into a leaf |
| gs | Stomatal conductance |
| gw | The internal conductance to the diffusion of CO2 between the intercellular air space and the site of carboxylation in the mesophyll cytoplasm |
| k | The ratio of oxygen atoms in the water to the oxygen atoms in CO2 |
| kCA | The hydration rate constant of CA |
| kt | The number of hydration reactions per CO2 molecule |
| pCO2 | Partial pressure of CO2 |
| pa | pCO2 of dry air in the atmosphere |
| pe | pCO2 of dry air entering the leaf chamber |
| pm | pCO2 of the mesophyll cytoplasm and site of CO2-H2O oxygen exchange |
| po | pCO2 of dry air leaving the leaf chamber |
| Re | 13C/12C of the air entering the leaf chamber |
| Ro | 13C/12C of the air leaving the leaf chamber |
| rb | Boundary layer resistance to water vapor diffusion (m2 s mol−1) |
| rs | Stomatal resistance to water vapor diffusion (m2 s mol−1) |
| θ | The proportion of CO2 in isotopic equilibrium with water at the site of oxygen exchange |
| ξ | pe/(pe − po) |
| τ | Residence time of CO2 in the leaf cytosol |