Regulation of Photosynthetic Light Energy Capture
37
o
(L
z
5
12
4
~
10
N~
8
rz
6
3
2
4
2
Hedera canariensis
O~~~----~--~~---L----~ 0
o
400
800
1200 1600 2000
-2 -1
PFD, j.4mol m s
r-...
0
~
x
0
0
~
'-"
c
..c
..... c
0
x
0
(I)
N
Fig. 2.12. Nonphotochemical fluorescence quenching (NPQ) and relative zeaxanthin content (Z) at steady state in relation to the PFD incident on a Hedera canariensis leaf. Z
formation was monitored by increases in leaf absorbance at 510nm (see Fig. 2.17). Leaf
temperature ranged from 25 to 29°C. (Based on data from Bilger and Bjorkman 1990)
2.5
7 r-... 0
;;;
..... 2.0
6 ~
c
(I)
x
E
0
n..
0
5
0
Q1
~
1.5
'-"
> (I)
4 c
-0
0
0
:;:;
0
(L
3 E
z 1.0
L
....
0
0
....
(I)
2 N
.....
....
0
0.5
0
cr:
,.
(I)
+'
Malva parviflora
0
cr:
0.0
0
5
10
15
20
25
30
35
Leaf temperature,OC
Fig. 2.13. Temperature dependence of the maximum rates of NPQ development and
zeaxanthin formation (Z) upon exposure of predarkened Malva parviflora leaves to a
PFD of 2000llmoi photons m- 2 s- 1 . These rates are the increases in NPQ and in the
absorbance at 510 nm obtained at 1.5 min after the onset to the light exposure. (After
Bilger and Bjorkman 1991)