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
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
Summary of Contents for LI-6400
Page 1: ...Using the LI 6400 Portable Photosynthesis System ...
Page 15: ...Part I The Basics ...
Page 16: ......
Page 174: ...Making Measurements Answers to Questions 4 56 Using the LI 6400 4 ...
Page 175: ...Part II Useful Details ...
Page 176: ......
Page 200: ...Standard Tools Power ON Hooks 5 24 Using the LI 6400 5 ...
Page 214: ...Real Time Data Real Time Graphics 6 14 Using the LI 6400 6 ...
Page 234: ...Environmental Control Light Control 7 20 Using the LI 6400 7 ...
Page 244: ...Light Sensor Considerations Gallium Arsenide Phosphide GaAsP Sensor 8 10 Using the LI 6400 8 ...
Page 288: ...Data Logging Making Your Own AutoPrograms 9 44 Using the LI 6400 9 ...
Page 289: ...Part III Working With Files ...
Page 290: ......
Page 312: ...The LPL File System Troubleshooting 10 22 Using the LI 6400 10 ...
Page 340: ...Downloading Files Using a Data Capture Program 11 28 Using the LI 6400 11 ...
Page 375: ...Part IV Configuration Issues ...
Page 376: ......
Page 420: ...Defining User Variables Old Style vs New Style 15 18 Using the LI 6400 15 ...
Page 454: ...Using an Energy Balance Further Reading 17 12 Using the LI 6400 17 ...
Page 455: ...Part V Maintenance Troubleshooting ...
Page 456: ......
Page 572: ...Troubleshooting Useful Information 20 46 Using the LI 6400 20 ...
Page 593: ...Part VI Programming ...
Page 594: ......
Page 622: ...Programming with LPL Compiler Directives 22 28 Using the LI 6400 22 ...
Page 846: ...Index I 16 Using the LI 6400 ...