Making Measurements
Leaks
4-46
Using the LI-6400
4
In order to correct photosynthesis calculations for the effects of CO
2
diffu-
sion, we re-visit the derivation of the photosynthesis equation. The mass bal-
ance equation ((1-11) on page 1-9) becomes
(4-2)
The
term accounts for diffusion. The final equation ((1-15) on
(4-3)
Note that there are now two Òcorrection termsÓ: one for transpiration, and one
for diffusion. The diffusion correction term is insignificant for measurements
with near-ambient CO
2
concentrations in the chamber (Table 4-2). Near the
CO
2
compensation point itÕs a different matter; diffusion becomes signifi-
Figure 4-11. Data from Figure 4-10 normalized by the CO
2
gradient, (C
a
- C
r
).
2
2
2
2
2
2
I
I
I
I
I
I
0
0.005
0.01
0
100
200
300
400
500
600
(C
s
- C
r
) / (C
a
- C
s
)
Flow Rate (µmol s
-1
)
0
250
600
2
1040
1570
I
2066
Normalized CO2 Diffusion
f(x) =
0.46
x
C
r
µmol mol
-1
sa
uc
i
uc
o
Ð
k c
a
c
o
Ð
(
)
+
=
k c
a
c
o
Ð
(
)
A
F C
r
C
s
Ð
(
)
100
S
---------------------------
C
s
E
Ð
k
100
S
------------
C
a
C
s
Ð
(
)
+
=
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 ...