CIRAS-3 Operation Manual V. 1.09
27
Placing the leaf inside the cuvette
Now would be a good time to get that small
tabletop tripod unless you prefer to hold the
leaf cuvette for upcoming measurements.
You will find a standard tripod thread on the
bottom of the leaf cuvette. Secure the
cuvette to the tripod and open the leaf
cuvette head and carefully place the leaf
inside the cuvette and close the cuvette as
shown here. Don’t be alarmed when you see
the CO2a and H2Oa values change causing
large fluctuations in CO2d and H2Od. This is
to be expected as you are temporarily
sampling ambient air which will likely be higher than your reference air for a brief moment. This will flush
through the system fairly quickly once you close the chamber head.
If possible it is best to fill the entire chamber window with your leaf to eliminate time consuming post-leaf
area analysis and recalculation of results. If the leaf fills the window completely then leaf area is clearly
defined and there will be no need to recalculate data based on leaf area.
What should I be looking for at this point?
With the leaf cuvette head closed on your leaf you should observe the following after about 5 seconds:
•
The CO2a and H2Oa will slowly return to previous levels and the CO2d will slowly approach 0
before going negative indicating CO
2
uptake resulting in positive Assimilation (A)
•
The H2Od value may also change quite dramatically but will also slowly approach 0 before going
positive indicating an increase in H
2
O due to leaf transpiration which should result in an increase
in stomatal conductance (gs) and evaporation or transpiration (E)
After approximately 45-60 seconds you should start to see the CO2d and H2Od values stabilize indicating
that the leaf has reached equilibrium. At this stage the Photosynthesis Data should also be very stable
as shown below.