22
O. Bjorkman and B. Demmig-Adams
1.0
no stress
0.8
""
C- 0.6
rn
a
'-'
0.4
stress
0.2
Stylosanthes humilis
0.0
9
12
15
18
Time of day
Fig. 2.4. Diurnal variation in the cosine of the leaf angle in relation to the solar beam in
leaves of Stylosanthes humilis, growing under well-watered conditions (no stress), and at
the beginning of the dry season (stress) during a cloudless day. The minimum water
potentials of the unstressed and stressed plants were -0.2 and -2.6MPa, respectively.
(Based on data from Begg and Torssell 1974)
1.0
._e-e-.
. . . . . . . . . -\
0.8
../
""
\
~ 1X=0.81
§
'-.1
i
Q)
()
c 0.6
0
......
a..
La
rn 0.4
.Q
0
.- .--.....
'<-~.~
0
Q)
1X=0.29 \
---1 0.2
Ence li a. jannosa
.~
•
0.0
' ---.
400
500
600
700
800
Wavelength, nm
Fig. 2.5. Spectral leaf absorptance (u) of a lightly pubescent, greenish, leaf and of a
heavily pubescent, white, leaf of Encelia farinosa. (Ehleringer and Bjorkman 1978)
O. Bjorkman and B. Demmig-Adams
1.0
no stress
0.8
""
C- 0.6
rn
a
'-'
0.4
stress
0.2
Stylosanthes humilis
0.0
9
12
15
18
Time of day
Fig. 2.4. Diurnal variation in the cosine of the leaf angle in relation to the solar beam in
leaves of Stylosanthes humilis, growing under well-watered conditions (no stress), and at
the beginning of the dry season (stress) during a cloudless day. The minimum water
potentials of the unstressed and stressed plants were -0.2 and -2.6MPa, respectively.
(Based on data from Begg and Torssell 1974)
1.0
._e-e-.
. . . . . . . . . -\
0.8
../
""
\
~ 1X=0.81
§
'-.1
i
Q)
()
c 0.6
0
......
a..
La
rn 0.4
.Q
0
.- .--.....
'<-~.~
0
Q)
1X=0.29 \
---1 0.2
Ence li a. jannosa
.~
•
0.0
' ---.
400
500
600
700
800
Wavelength, nm
Fig. 2.5. Spectral leaf absorptance (u) of a lightly pubescent, greenish, leaf and of a
heavily pubescent, white, leaf of Encelia farinosa. (Ehleringer and Bjorkman 1978)