40
E
0
~
I (5
E
(5
E
E
.•. ;
c
Q)
...,
c
0
0
"U
'0
c
Q)
...,
0
L0
0
O. Bjorkman and B. Demmig-Adams
200
Lutein
160
is.
120
80
40
Neoxanthin
o ~ __ ~ __ ~ __ L -_ _ L -_ _ ~ _ _ ~~
o 10 20 30 40 50 60 70
-2
Daily photon receipt, mol m
Fig. 2.15. Influence of the daily photon receipt during the development of cotton cotyledons on the pool size of the xanthophyll cycle pigments (V + A + Z) and the contents
of other major carotenoids, expressed on a chlorophyll a + b basis. (Chlorophyll content
per unit leaf area was little affected over this range of photon receipts.) Experiments were
conducted in the field at Stanford, California in June-July, 1989. Attenuation of the
photon receipt was obtained by shading the seedlings with neutral-density filters of
varying transmittance. (Original data by O. Bjorkman and C. Shih)
:c
200
0
I" 160
0
E
(5
E 120
E
~
c
Q)
80
+'
C
0
()
-0
'0
40
c
/~
/
~
V+A+Z ~"Y
"Y~~
/~
"Y~
"Y~+A+Z
/"Y
Neoxanthin
Neoxanthin ~
'V'--'"
-=Q)
.....
0
La
0
0 o
2
3
4
5
6
7 0
2
3
4
5
6
7
Days after exposure to full sun
Days after shading
Fig. 2.16. Dynamic responses of the V + A + Z pool size and the contents of lutein and
neoxanthin to sudden changes in light regime. In the left panel the daily photon receipt
was increased from 3.6 to 58 mol photons m- 2 d- 1 and in the right panel it was decreased
from 58 to 3.6mol photons m- 2 d- 1 . Other conditions were as in Fig. 2.15. (Original data
by O. Bjorkman and C. Shih)