Walz MINI-PAM-II, Manual, Page: 45 / 130

Saturation Pulse Analysis Chapter 5
39
sorbed. The ETR-Factor can be lower in bleached leaves or
leaves containing considerable amounts of non-photosynthetic
pigments like anthocyanins.
(3) P
PS2
/P
PS1+2
Relative distribution of absorbed PAR to photo-
system II
The default P
PS2
/P
PS1+2
is 0.5 which assumes the PS II contrib-
utes 50% to total sample absorptance. The P
PS2
/P
PS1+2
may de-
viate from the idealized factor of 0.5 depending on wavelength of
light and acclimation status of the sample.
5.4 Light Curves
The light curve program exposes a sample to stepwise increas-
ing intensities of actinic illumination. In “Rapid Light Curves”
(RLC), the time interval of each light step is short (down to 10 s)
and full equilibration of photosynthetic reactions is not reached
within an illumination interval. Typically, the RLC starts at a PAR
value somewhat below that of the natural environment.
RLC measurements are carried out with samples in their mo-
mentary acclimation status, that is, without dark-acclimation peri-
od to determine F
0
and F
M
. This way, RLC data can provide in-
formation on the present acclimation state of photosynthesis.
Obviously, without F
0
and F
M
determination, those fluorescence
ratio parameters requiring F
0
and F
M
(like NPQ and qP) are not
available.
If illumination steps are long enough to reach steady state of
photosynthesis, fluorescence-based light curves may be com-
pared with classical light response curves (P-I curves). Naturally,
any limitation by insufficient CO
2
supply must be avoided during
such long-term light curves.