Leaf Porometer Operator’s Manual
6. Leaf Porometer Theory
60
where
is the molar density of air and
D
vapor
is the
diffusivity of water vapor. Both of these quantities are
temperature and pressure dependent, however when
multiplied together as in equation (3) some of this
dependency drops out:
Using these
C
and
g
values we can now solve equation 1 for
the flux:
(8)
Now that the vapor flux has been determined, the stomatal
conductance,
g
s
, can be found. This requires some
assumptions. First, we assume that the relative humidity
within the leaf tissue is 1.0, so by equation
(9)
75
.
0
5
2
5
75
.
1
15
.
273
)
10
12
.
2
)(
6
.
44
(
ˆ
)
/
(
10
12
.
2
)
3
.
101
,
15
.
273
(
15
.
273
3
.
101
)
3
.
101
,
15
.
273
(
)
,
(
15
.
273
3
.
101
6
.
44
ˆ
=
=
=
=
−
−
T
x
D
Then
s
m
x
D
If
T
P
D
P
T
D
T
P
vapor
ref
a
ref
a
vapor
a
ρ
ρ
(5)
(6)
(7)
atm
a
s
leaf
p
T
e
C
)
(
=