System Description
The Flow Schematic
1-6
Using the LI-6400
1
Matching the IRGAs
The heart of the computation of transpiration and assimilation is the measure-
ment of the concentration differences. Since these differences are measured
by two independent gas analyzers, provisions must be made to check the IR-
GAs against one another. One way to do this is to compare the IRGAs when
the leaf chamber is empty, and adjust one so that they match. Matching in this
manner is a problem, however, because you donÕt want to remove the leaf
from the chamber in the middle of an experiment. The LI-6400 provides a
mechanism to match the IRGAs without disturbing the leaf: it is called match
mode, and it is illustrated in Figure 1-3.
Match mode is something that you do at least once at the start of the day, and
periodically throughout the day. Matching is important when the
D
CO
2
or
D
H
2
O value is small (low rates, small leaf areas). For example, a
1 µmol mol
-1
offset between the two CO
2
IRGAs is trivial when the
D
CO
2
is
75 µmol mol
-1
, but represents a significant error if the
D
CO
2
is only
3 µmol mol
-1
.
Figure 1-3. In Match Mode, leaf chamber air is measured by both sample and ref-
erence IRGAs, allowing the sample IRGA to be adjusted to match the reference IR-
GA.
Sample
Reference
Normal
Sample
Reference
Match
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 ...