It is known that the characteristic O–I–P transient of the fast
chlorophyll a fluorescence rise (FR) detected under low
intensity of exciting light, changes to the O–J–I–P
(O–I 1 –I 2 –P)
transient under higher intensity of exciting light. In this work, we extend an
application of the mathematical model of FR [Lazár
et al. (1997)l
Pesticide Biochemistry and Physiology
57, 200–210], involving photosystem II
(PSII) heterogeneity and simulating the O–J–I–P transient,
for modeling of FR under different intensities of exciting light. Our
simulations qualitatively agree well with experimental FR curves obtained with
wheat leaves. The simulations demonstrate that the first step after the O
fluorescence level (the I step and the J step under lower and higher
intensities of exciting light, respectively) is caused mainly by the
accumulation of reduced QA electron acceptors without
reduction of subsequent electron acceptors. The first step appears at shorter
times with increasing intensity of exciting light as reported previously
[Strasser et al. (1995)
Photochemistry and Photobiology 61,
32–42]. Our simulations also demonstrate, in accordance with
previous publications, that the O–I phase in FR detected under low
intensity of exciting light, reflects mainly the accumulation of Q
A – in the Q
B-non-reducing PSII centers and partly also the
accumulation of Q A – in the
Q B -reducing PSII centers. In our model, the
accumulation of Q A – in the
Q B -non-reducing PSII centers gradually shifts with
increasing intensity of exciting light to shorter times and participates in
the formation of the O–J phase; this is also supported by measurements
of FR with wheat leaves treated with
3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU). Under high
intensity of exciting light, the O–J phase in FR also markedly reflects
the accumulation of Q A – in
the Q B -reducing PSII centers. Our simulations also
support the previously reported suggestion of Strasser’s group that the
I step in FR obtained under high intensity of exciting light (in the position
of the I step detected under lower intensity of exciting light) appears mainly
owing to the accumulation of the Q A
–Q B
2– and Q
A–Q BH
2f orms.
Remote sensing of sun-induced chlorophyll-a fluorescence in inland and coastal waters: Current state and future prospects
