Leaf Porometer Operator’s Manual
6. Leaf Porometer Theory
62
Using the rule for series combination of conductance, we
can solve for g
s
:
(14)
Hence,
(15)
so:
(16)
Therefore, g
s
is a function of the distances between
humidity sensors, temperature, and the two relative
humidity readings.
When the conductance is small, the humidities are nearly
the same, and the denominator of the denominator of eq. 6
goes to zero, causing problems. Multiplying top and bottom
by the denominator gives
(17)
NOTE:
The resulting g
s
is in units of mol/m
2
s.
1
1
1
1
1
d
d
s
s
g
g
g
−
=
+
[
]
D
d
T
e
h
T
e
h
D
d
h
T
e
g
a
s
r
a
s
r
r
a
s
s
ρ
ρ
ˆ
)
(
)
(
ˆ
)
1
)(
(
1
1
2
2
1
1
2
1
1
−
−
−
=
[
]
1
2
2
1
1
2
1
1
)
(
)
(
)
1
)(
(
ˆ
d
T
e
h
T
e
h
d
h
T
e
D
g
a
s
r
a
s
r
r
a
s
vapor
s
−
−
−
=
ρ
[
]
1
2
2
1
1
2
1
1
2
2
1
1
)]
(
)
(
[
)
1
)(
(
)]
(
)
(
[
ˆ
d
T
e
h
T
e
h
d
h
T
e
T
e
h
T
e
h
D
g
a
s
r
a
s
r
r
a
s
a
s
r
a
s
r
vapor
s
−
−
−
−
=
ρ
