Diurnal Response of Photosystem I to Fluctuating Light Is Affected by Stomatal Conductance

Abstract

Upon a sudden transition from low to high light, electrons transported from photosystem II (PSII) to PSI should be rapidly consumed by downstream sinks to avoid the over-reduction of PSI. However, the over-reduction of PSI under fluctuating light might be accelerated if primary metabolism is restricted by low stomatal conductance. To test this hypothesis, we measured the effect of diurnal changes in stomatal conductance on photosynthetic regulation under fluctuating light in tomato (Solanum lycopersicum) and common mulberry (Morus alba). Under conditions of high stomatal conductance, we observed PSI over-reduction within the first 10 s after transition from low to high light. Lower stomatal conductance limited the activity of the Calvin–Benson–Bassham cycle and aggravated PSI over-reduction within 10 s after the light transition. We also observed PSI over-reduction after transition from low to high light for 30 s at the low stomatal conductance typical of the late afternoon, indicating that low stomatal conductance extends the period of PSI over-reduction under fluctuating light. Therefore, diurnal changes in stomatal conductance significantly affect the PSI redox state under fluctuating light. Moreover, our analysis revealed an unexpected inhibition of cyclic electron flow by the severe over-reduction of PSI seen at low stomatal conductance. In conclusion, stomatal conductance can have a large effect on thylakoid reactions under fluctuating light.

Exogenous melatonin strongly affects dynamic photosynthesis and enhances water-water cycle in tobacco

“…The resulting PSI over-reduction induces PSI photoinhibition under fluctuating light ( Suorsa et al, 2012 ; Yamamoto and Shikanai, 2019 ). Furthermore, a decreased g s could aggravate the extent of PSI over-reduction under fluctuating light ( Li T. Y. et al, 2021 ). Upon a sudden transitioning from low to high light, alternative electron sinks can rapidly consume the reducing power in PSI and thus prevents PSI over-reduction ( Gerotto et al, 2016 ; Jokel et al, 2018 ; Storti et al, 2019 , 2020 ).…”

Differential Response of the Photosynthetic Machinery to Fluctuating Light in Mature and Young Leaves of Dendrobium officinale

“…Generally, the induction speed of PSII electron flow is faster than that of CO 2 assimilation in photosynthetic organisms, leading to the accumulation of excited states in PSI when light intensity abruptly changes from low to high (Gerotto et al, 2016;Li et al, 2021). Meanwhile, photosynthetic angiosperms cannot generate a sufficient pH (Huang et al, 2019a;Yang et al, 2021a), leading to a temporary uncontrolled electron flow from PSII to PSI through the Cyt b6f complex Armbruster et al, 2017).…”

Physiological and molecular mechanisms regulated mesophyll conductance under severe drought in water-saving drought-resistant rice

“…The results could indicate that g s is more sensitive to severe drought than g m and g m is main factor to regulate P n in severe drought of rice plants. The founds are basically consistent with previous studies that maintaining high g m is key to obtain high P n in drought (Ouyang et al ., 2017; He et al ., 2021; Li et al ., 2021).…”

“…When CO 2 concentration at carboxylase site is restricted by low g s or g m in adverse environmental conditions, the amount of NADP + , which was regenerated in tricarboxylic acid cycle processes of photosynthesis, would be limited because of inadequate CO 2 supply capacities. And then adjusting energy redistribution in PSII and PSI systems to avoid photoinhibition and photo-damage of the both photosystems (Zivcak et al ., 2013; Li et al ., 2021). In addition, low g m in stress restrain carboxylation rate and regeneration of ribulose diphosphate, electron transport in PSII is impaired in the circumstances (Killi and Haworth, 2017).…”