PP Systems TARGAS-1 - Definition of Symbols and Physical Constants Used in Equations

TARGAS-1 Operation Manual V. 1.02 154 support@ppsystems.com
Definition of Symbols and Physical Constants Used in Equations
Measured Parameters
Symbol
Parameter
Unit


Flow rate of dry air into cuvette at STP
cc min
-1

Projected leaf area
cm
2


Boundary layer resistance to water vapor
m
2
s mol
-1

Atmospheric pressure
mb

Photon flux density incident on cuvette
µmol m
-2
s
-1


Cuvette air temperature
°C
Calculated Parameters
Symbol
Parameter
Unit

Mass flow of air per unit leaf area into cuvette
mol m
-2
s
-1


Partial pressure of water vapor of air entering cuvette = H
2
Or
mb *


Partial pressure of water vapor of stirred cuvette air = H
2
Oa
mb *

Transpiration rate
mmol m
-2
s
-1


Saturated vapor pressure (inside the leaf) at leaf temperature
mb


Leaf temperature
°C

Temperature difference between the air and the leaf
°C

Radiation absorbed by the leaf
W m
-2


Stomatal resistance to water vapor
m
2
s mol
-1


Stomatal conductance to water vapor
mmol m
-2
s
-1


CO
2
concentration of air entering cuvette = CO
2
r
µmol mol
-1
*


CO
2
concentration of air inside and exiting the cuvette = CO
2
a
µmol mol
-1
*

CO
2
Assimilation rate (net photosynthesis)
µmol m
-2
s
-1


Total conductance to CO
2
transfer
mmol m
-2
s
-1


Total conductance to H
2
O transfer
mmol m
-2
s
-1


CO
2
concentration of sub-stomatal cavity
µmol mol
-1
* Detected by IRGAs, temperature and pressure corrected, effects of foreign gas broadening (water vapor
effects) on measurement corrected.
Physical Constants
Symbol
Parameter
Value

Latent heat of vaporization of water
45064.3 - (T
c
x 42.9) J mol
-1


Molecular mass of air
28.97


Specific heat at constant pressure
1.012 kJ kg
-1
K
-1

Stefan Boltzmann constant
5.6704 x 10
-8
W m
-2
K
-4