Gradients of Photoinhibition in the Interior of a Leaf Induced by Photoinhibition Lights of Different Colors

Photodamage to Photosystem II (PSII) has been attributed either to excessive excitation of photosynthetic pigments or by direct of light absorption by Mn4CaO5 cluster. Here we investigated the time course of PSII photodamage and release of Mn in PSII-enriched membranes under high light illumination at 460 nm and 660 nm. We found that the loss of PSII activity, assayed by chlorophyll fluorescence, is faster than release of Mn from the Mn4CaO5 cluster, assayed by EPR. Loss of PSII activity and Mn release was slower during illumination in the presence of exogenous electron acceptors. Recovery of PSII activity was observed, after 30 min of addition of electron donor post illumination. The same behavior was observed under 460 and 660 nm illumination, suggesting stronger correlation between excessive excitation and photodamage compared to direct light absorption by the cluster. A unified model of PSII photodamage that takes into account present and previous literature reports is presented.

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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

Iermak¹,

Szabó²,

Zavafer³

2020

Photosynt.

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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.

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Gradients of Photoinhibition in the Interior of a Leaf Induced by Photoinhibition Lights of Different Colors

Cited by 3 publications

References 15 publications

Plasticity of the Photosynthetic Energy Conversion and Accumulation of Metabolites in Plants in Response to Light Quality

Plasticity of the Photosynthetic Energy Conversion and Accumulation of Metabolites in Plants in Response to Light Quality

Mechanism of Photodamage of the Oxygen Evolving Mn Cluster of Photosystem II by Excessive Light Energy

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

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