Elevated CO2 Concentration Alters Photosynthetic Performances under Fluctuating Light in Arabidopsis thaliana.

Shun-Ling Tan,Wei Huang,Xing Huang,Wei-Qi Li,Shi-Bao Zhang

doi:10.3390/cells10092329

Shun-Ling Tan, Wei Huang + Show 3 more

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https://doi.org/10.3390/cells10092329

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Abstract

In view of the current and expected future rise in atmospheric CO2 concentrations, we examined the effect of elevated CO2 on photoinhibition of photosystem I (PSI) under fluctuating light in Arabidopsis thaliana. At 400 ppm CO2, PSI showed a transient over-reduction within the first 30 s after transition from dark to actinic light. Under the same CO2 conditions, PSI was highly reduced after a transition from low to high light for 20 s. However, such PSI over-reduction greatly decreased when measured in 800 ppm CO2, indicating that elevated atmospheric CO2 facilitates the rapid oxidation of PSI under fluctuating light. Furthermore, after fluctuating light treatment, residual PSI activity was significantly higher in 800 ppm CO2 than in 400 ppm CO2, suggesting that elevated atmospheric CO2 mitigates PSI photoinhibition under fluctuating light. We further demonstrate that elevated CO2 does not affect PSI activity under fluctuating light via changes in non-photochemical quenching or cyclic electron transport, but rather from a rapid electron sink driven by CO2 fixation. Therefore, elevated CO2 mitigates PSI photoinhibition under fluctuating light at the acceptor rather than the donor side. Taken together, these observations indicate that elevated atmospheric CO2 can have large effects on thylakoid reactions under fluctuating light.

Highlights

Photosynthetic organisms absorb light energy to drive photosynthetic electron flow and CO2 assimilation
The rapid re-oxidation of P700 after transition from darkness to light is attributed to the outflow of electrons from photosystem I (PSI) to downstream electron acceptors [43,44,45]
We concluded that the effects of elevated CO2 concentration on PSI redox state are not caused by electron flow from photosystem II (PSII) or the formation of a ∆pH

Summary

Introduction

Photosynthetic organisms absorb light energy to drive photosynthetic electron flow and CO2 assimilation. In linear electron flow (LEF), electrons are transferred from photosystem II (PSII) to photosystem I (PSI), and to NADP+, producing NADPH. This electron flow is coupled to the formation of proton motive force that powers the regeneration of ATP. In cyclic electron flow (CEF) around PSI, electrons are transported from ferredoxin into the plastoquinone pool, generating ATP without producing NADPH. Once PSI is photodamaged, as indicated by the decrease in the maximum photo-oxidizable P700 (Pm), both LEF and CEF are depressed, which will affect CO2 fixation and impair plant growth [2,3,4,5,6]

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