Growth under Fluctuating Light Reveals Large Trait Variation in a Panel of Arabidopsis Accessions.

Shinya Wada,Yuji Suzuki,Chikahiro Miyake

doi:10.3390/plants9030319

Shinya Wada, Yuji Suzuki + Show 1 more

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https://doi.org/10.3390/plants9030319

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Abstract

The oxidation of P700 in photosystem I (PSI) is a robust mechanism that suppresses the production of reactive oxygen species. We researched the contribution of photorespiration to the oxidation of P700 in wheat leaves. We analyzed the effects of changes in partial pressures of CO2 and O2 on photosynthetic parameters. The electron flux in photosynthetic linear electron flow (LEF) exhibited a positive linear relationship with an origin of zero against the dissipation rate (vH+) of electrochromic shift (ECS; ΔpH across thylakoid membrane), indicating that cyclic electron flow around PSI did not contribute to H+ usage in photosynthesis/photorespiration. The vH+ showed a positive linear relationship with an origin of zero against the H+ consumption rates in photosynthesis/photorespiration (JgH+). These two linear relationships show that the electron flow in LEF is very efficiently coupled with H+ usage in photosynthesis/photorespiration. Lowering the intercellular partial pressure of CO2 enhanced the oxidation of P700 with the suppression of LEF. Under photorespiratory conditions, the oxidation of P700 and the reduction of the plastoquinone pool were stimulated with a decrease in JgH+, compared to non-photorespiratory conditions. These results indicate that the reduction-induced suppression of electron flow (RISE) suppresses the reduction of oxidized P700 in PSI under photorespiratory conditions. Furthermore, under photorespiratory conditions, ECS was larger and H+ conductance was lower against JgH+ than those under non-photorespiratory conditions. These results indicate that photorespiration enhances RISE and ΔpH formation by lowering H+ conductance, both of which contribute to keeping P700 in a highly oxidized state.

Highlights

Plants, both wild and cultivated, face the threat of oxidative damage from reactive oxygen species (ROS) when they are exposed to environments in which photosynthesis is suppressed [1].For example, low temperatures, high temperatures, and dryness promote stomata closure, which reduces photosynthesis abilities [2]
P700 is oxidized by the limitation of electron flow to the oxidized form of
P700, P700+ [1], and +the oxidation activity of PQH2 of the cytochrome b6 /f complex is down-regulated by form of P700, P700 [1], and the oxidation activity of PQH2 of the cytochrome b6/f complex is downthe acidification of the luminal space and reduction-induced suppression of electron flow (RISE)

Summary

Introduction

Low temperatures, high temperatures, and dryness promote stomata closure, which reduces photosynthesis abilities [2]. In these circumstances, superoxide radicals (O2 − ) can be generated through the photoreduction of O2 − in photosystem I (PSI), and H2 O2 is generated by the Plants 2020, 9, 319; doi:10.3390/plants9030319 www.mdpi.com/journal/plants. The photoreduction of O2 in PSI is regarded as the main ROS-generating process in photosynthetic organisms exposed to environmental stresses [2]. These ROS increase the risk of oxidative damage. To imitate situations in which electrons accumulate on the PSI acceptor side—situations of environmental stress that lowers photosynthesis efficiency and NADP+ regeneration efficiency—the leaves of sunflower plants were illuminated intermittently with saturating lights in darkness (repetitive short-pulse (rSP)

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