EQUATIONS TO CALCULATE PHOTOSYNTHESIS
Transpiration.-
Fd·e K Fd de
------- + [----------------] [Vt - ---- Vg] ----
100·P 8.314 (Ta + 273) Fx dt
E = ------------------------------------------------------
e
S [1 - --- ]
P
Where:
Ta= Chamber air temperature (°C).
Fd= Flow through desiccant µmol/s.
e= Vapor pressure of air (mb).
de/dt= Rate of change of e.
E= Transpiration rate (mol/m²/s).
P= Atmospheric pressure (mb).
S= Leaf area (cm²).
Vt= Total volume (cm3).
Fx= Max flow rate (µmol/s).
Vg= IRGA volume (cm3).
K= Absorption coefficient.
Stomatal Conductance.-
The equation to determine the stomatal conductance to water vapor
takes into account the convective effect at the stomatal pores caused by
the transpiration.
1
gsw = ---------------------
A - B
es(Tl) - e
A = -------------------------
es(Tl) + e
E [P - ------------ ] 2
2
(K² + 1)
B = ------------------
gbwo (K + 1)²
2
Where:
gsw in mol m²/s
Tl= Leaf temperature (°C).
e= Vapor pressure in chamber (mb).
es= Saturation vapor pressure function (mb)
gbwo= One side boundary layer conductance (mol/m²/s).
K= Stomatal ratio.
Photosynthesis.-
In this case the term (dc/dt) is included to simulate transient conditions in a closed system.
Fd · e · C P· G · Vt dc
A = -------------- - -------------------- - ---- - C·E·G
100 · S · P 8.314 (Ta + 273) S dt
Where:
A in µmol/m²/s
C= CO2 concentration (µl/l)
Intercellular CO2 Content.-
E
[ gtc - --- Ca - A ]
2
Ci = -------------------------
E
[ gtc + --- ]
2
Where:
gtc= Total conductance to CO2
The total conductance to CO2 is calculated from the conductances for water vapor:
1 1.6 1.37
--- = ----- + ------
gtc gsw gbw
Where:
1.37= Ratio of diffusivities of CO2 and water vapor in
the boundary layer.
1.6= Ratio of diffusivities of CO2 and water vapor in air.
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