PP Systems CIRAS-2 - Step 5.0; Step 6.0

Appendix 3. Photosynthesis Equations Used in CIRAS-2
CIRAS-2 Operator's Manual Version 2.04
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(4.5) Then,
(4.6) It follows that stomatal conductance is the inverse of stomatal resistance:
Step 5.0
Determine the rate of net photosynthesis (A) from the difference between CO
2
concentrations
entering (C
in
) and leaving (C
out
) the cuvette
(5.1) IRGA CO
2
readings are corrected for water vapor, temperature, and atmospheric pressure. The
addition of transpirational water vapor dilutes the air leaving the cuvette (C
out
), and this is compensated for
in the calculation:
(5.2) Therefore,
CIRAS-2 calculates and displays the CO
2
difference (C
out
- C
in
). As relates to the calculated values in the
CIRAS-2 display:
Step 6.0
Calculate CO
2
concentration in the sub-stomatal cavity (C
i
) using the equation derived by von
Caemmerer & Farquhar (Reference 3)
(6.1)