Elevated CO₂ Concentration Alters Photosynthetic Performances under Fluctuating Light in <i>Arabidopsis thaliana</i>

• Main Authors: Shun-Ling Tan, Xing Huang, Wei-Qi Li, Shi-Bao Zhang, Wei Huang
• Format: Article
• Language: English
• Published: MDPI AG 2021-09-01
• Series: Cells
• Subjects: CO₂ concentration; photosynthesis; photosystem I; redox state of P700
• Online Access: https://www.mdpi.com/2073-4409/10/9/2329

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 <i>Arabidopsis thaliana</i>. 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.