LI-COR LI-6400, Руководство пользователя

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Making Measurements
CO2 Response Curves
Using the LI-6400 4-31
erence value, you could also run the mixer in the constant control signal mode
(option C). If you do, youÕll be entering the target values for the AutoProgram
in mV instead of µmol mol
-1
.
In what order should the curve be measured? There are a couple of constraints
to consider. One is that high CO
2
concentrations may induce some stomatal
closure, so if you are including high CO
2
, they should be done last. The other
constraint is that if too much time is spent near the CO
2
compensation point,
enzyme deactivation may occur. A suggested measurement scheme is to start
at ambient, got down to the compensation point, return to ambient, then in-
crease to the upper limit.
Temperature
The response curve should be measured under constant temperature condi-
tions. Operate the coolers for a constant leaf temperature.
Humidity Control
Operate the flow control for constant water mole fraction. Expect higher con-
ductances and transpiration rates at the low CO
2
values, so leave room for the
flow rate to increase.
Matching
Since the concentrations of CO
2
are covering a large range, match before
each reading.
With OPEN version 3.2 and above, you are asked for a matching threshold
(the absolute value of the
D
CO
2
value). Thus, you donÕt have to decide
whether to match before each observation or not; it will match on the ones
with
D
CO
2
smaller than your threshold, and skip the rest.
Diffusion
This can be a problem for A-Ci curves, since there can be a large gradient be-
tween the chamber and ambient. See
Diffusion Leaks on page 4-43.
Real Time Graphics
Two useful pre-defined real time graphics configurations are
"A-Ci, RH_Flow, totalCV"
"A-Ci, totalCV, CO2S"
The first one is recommended, since it shows photosynthesis as a function of
intercellular CO
2
. It also contains the RH-Flow plot that lets you monitor the