Temperature effects on pea plants probed by simultaneous measurements of the kinetics of prompt fluorescence, delayed fluorescence and modulated 820 nm reflection.

Abdallah Oukarroum,Vasilij Goltsev,Reto J Strasser,Rajagopal Subramanyam

doi:10.1371/journal.pone.0059433

Abdallah Oukarroum, Vasilij Goltsev + Show 2 more

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https://doi.org/10.1371/journal.pone.0059433

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Abstract

Simultaneous in vivo measurements of prompt fluorescence (PF), delayed fluorescence (DF) and 820-nm reflection (MR) were made to probe response of pea leaves to 40 s incubation at high temperatures (25–50°C). We interpret our observation to suggest that heat treatment provokes an inhibition of electron donation by the oxygen evolving complex. DF, in a time range from several microseconds to milliseconds, has been thought to reflect recombination, in the dark, between the reduced primary electron acceptor QA – and the oxidized donor (P680+) of photosystem II (PSII). The lower electron transport rate through PSII after 45 and 50°C incubation also changed DF induction. We observed a decrease in the amplitude of the DF curve and a change in its shape and in its decay. Acceleration of P700+ and PC+ re-reduction was induced by 45°C treatment but after 50°C its reduction was slower, indicating inhibition of photosystem I. We suggest that simultaneous PF, MR and DF might provide useful information on assessing the degree of plant tolerance to different environmental stresses.

Highlights

Simultaneous chlorophyll (Chl) a fluorescence and 820-nm transmission measurements have provided strong experimental evidence that the three phases (i.e. O-J, J-I and I-P) of the prompt fluorescence rise OJIP [1] reflect three different reduction processes of the electron transport chain [2,3,4]
prompt fluorescence (PF) depends on the redox state of the photosystem II (PS II) reaction centers (RC); the delayed fluorescence emission (DF) in a time range from several microseconds to milliseconds, after light excitation, has been thought to reflect the recombination, in the dark, between the reduced primary electron acceptor QA– and the oxidized donor (P680+) of photosystem II (PSII) that are formed after light-induced charge separation [8]
We have shown that simultaneous measurement of PF, DF and modulated nm reflection (MR) is an important tool to characterize the effect of high temperature on intact photosynthetic systems and can be used as a tool to monitor these changes induced in the photosynthetic membranes

Summary

Introduction

Simultaneous chlorophyll (Chl) a fluorescence and 820-nm transmission measurements have provided strong experimental evidence that the three phases (i.e. O-J, J-I and I-P) of the prompt fluorescence rise OJIP [1] reflect three different reduction processes of the electron transport chain [2,3,4]. DF was discovered by Strehler and Arnold [6] It is mainly emitted from photosystem II (PS II), and photosystem I (PS I) contributes very little to the DF emission [7]. PF depends on the redox state of the PS II reaction centers (RC); the DF in a time range from several microseconds to milliseconds, after light excitation, has been thought to reflect the recombination, in the dark, between the reduced primary electron acceptor QA– and the oxidized donor (P680+) of PSII that are formed after light-induced charge separation [8]. DF has been thought to reflect the recombination between the reduced electron acceptor QA– and the oxidized secondary electron donor, Z+, of PSII [9]. In the second time range, DF is associated with the recombination of S2 and S3 states of the oxygen-evolving complex (OEC) with QA– and QB– [10,11,12]

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