*This paper is dedicated to Warren L. Butler on the occasion of his 70th birthday, which would have been on 28 January 1995.
POLYPHASIC CHLOROPHYLL a FLUORESCENCE TRANSIENT IN PLANTS AND CYANOBACTERIA*
Article first published online: 2 JAN 2008
Photochemistry and Photobiology
Volume 61, Issue 1, pages 32–42, January 1995
How to Cite
Strasserf, R. J., Srivastava, A. and Govindjee (1995), POLYPHASIC CHLOROPHYLL a FLUORESCENCE TRANSIENT IN PLANTS AND CYANOBACTERIA. Photochemistry and Photobiology, 61: 32–42. doi: 10.1111/j.1751-1097.1995.tb09240.x
- Issue published online: 2 JAN 2008
- Article first published online: 2 JAN 2008
- Received 22 July 1994; accepted 12 September 1994)
Abstract— The variable chlorophyll (Chl) a fluorescence yield is known to be related to the photochemical activity of photosystem II (PSII) of oxygen-evolving organisms. The kinetics of the fluorescence rise from the minimum yield, F0, to the maximum yield, Fm, is a monitor of the accumulation of net reduced primary bound plastoquinone (QA) with time in all the PSII centers. Using a shutter-less system (Plant Efficiency Analyzer, Hansatech, UK), which allows data accumulation over several orders of magnitude of time (40 μs to 120 s), we have measured on a logarithmic time scale, for the first time, the complete polyphasic fluorescence rise for a variety of oxygenic plants and cyanobacteria at different light intensities. With increasing light intensity, the fluorescence rise is changed from a typical O-I-P characteristic to curves with two intermediate levels J and I, both of which show saturation at high light intensity but different intensity dependence. Under physiological conditions, Chl a fluorescence transients of all the organisms examined follow the sequence of O-J-I-P. The characteristics of the kinetics with respect to light intensity and temperature suggest that the O-J phase is the photochemical phase, leading to the reduction of QA to QA-. The intermediate level I is suggested to be related to a heterogeneity in the filling up of the plastoquinone pool. The P is reached when all the plastoquinone (PQ) molecules are reduced to PQH2. The addition of 3-(3–4-dichlorophenyl)-1,1-dimethylurea leads to a transformation of the O-J-I-P rise into an O-J rise. The kinetics of O-J-I-P observed here was found to be similar to that of O-I1-I2-P, reported by Neubauer and Schreiber (Z. Naturforsch.42c, 1246–1254, 1987). The biochemical significance of the fluorescence steps O-J-I-P with respect to the filling up of the plastoquinone pool by PSII reactions is discussed.