PHOTOSYNTHETICA

Photosynthetica 2020, 58(SI):497-506 | DOI: 10.32615/ps.2019.166

Special issue in honour of Prof. Reto J. Strasser – Analysis of OJIP transients during photoinactivation of photosystem II indicates the presence of multiple photosensitizers in vivo and in vitro

I. IERMAK^1,2,3, M. SZABÓ^5,6, A. ZAVAFER⁷

¹ Laboratory of Biophysics, Wageningen University, P.O. Box 8128, 6700 ET, Wageningen, The Netherlands

² BioSolar Cells Project Office, P.O. Box 98, 6700 AB, Wageningen, The Netherlands

³ São Carlos Institute of Physics, University of São Paulo, São Carlos, SP, Brazil

⁵ Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, 6726 Szeged, Hungary

⁶ Climate Change Cluster, University of Technology Sydney, Ultimo 2007, Australia

⁷ Research School of Biology, College of Medicine, Biology and Environment, The Australian National University, Canberra ACT 2601, Australia

Generally, excessive excitation absorbed by the pigments is considered the cause of PSII photodamage. Previous studies of action spectra of PSII photodamage concluded that shorter wavelengths induce more damage, supporting the hypothesis of the existence of more than one photosensitizer. However, the relative influence of different photosensitizers is still inconclusive. In this work, we have revisited this question by inducing PSII photodamage in vivo and in vitro at two different wavelengths (460 and 660 nm) where the net absorption cross section was the same using equal irradiance. To correlate PSII photodamage with each wavelength band, we followed its time course using the OJIP transient of the chlorophyll fluorescence to determine the possible contributions of photoinhibition by different photosensitizers. We found evidence that at least two sites of photoinactivation of PSII exist.

Additional key words: absorptance; chlorophyll fluorescence; manganese cluster; photodamage; spinach; two-photon excitation microscopy.

Received: August 28, 2019; Revised: November 21, 2019; Accepted: December 6, 2019; Prepublished online: March 6, 2020; Published: May 28, 2020  Show citation