Is bicarbonate directly used as substrate to participate in photosynthetic oxygen evolution

Abstract

If the photosynthetic organisms assimilated only CO2 in the Archean atmosphere, hydroxide ion in the Archean seawater would not increase. If plants would not consume bicarbonate as a direct substrate during photosynthesis, it is difficult to explain the evolution of Earth's environment. To date, it is generally accepted that photosynthetic O2 evolution of plants come from water photolysis. However, it should be debated by evaluating the effect of bicarbonate in photosynthetic O2 evolution, analyzing the role of carbonic anhydrase (CA) in photosynthetic O2 evolution, and the relationship between thylakoid CA and photosynthetic O2 evolution. In the paper, I propose that bicarbonate is directly used as substrate to participate in photosynthetic O2 evolution. The rationality of bicarbonate photolysis of plants is discussed from the thermodynamics and evolution of Earth's environment. The isotopic evidence that bicarbonate is not the direct substrate of photosynthetic O2 release is reexamined, and the new explanation of bicarbonate photolysis in photosynthetic O2 evolution is proposed.

Comprehensive Analyses of the Enhancement of Oxygenesis in Photosynthesis by Bicarbonate and Effects of Diverse Additives: Z-scheme Explanation versus Murburn Model

“…We would like to point out that the accurate Gibbs free energy calculations we report here are much higher than the misplaced earlier values reported in literature [14,70], which give 103.8 and 156.1 kJ/mol respectively for reactions ( 14) and ( 15), for the same ½O 2 stoichiometry. The difference is also seen in relative terms (for bicarbonate versus water); our calculations showing a difference of $36 kJ/mol compared to Dismukes' differential of $52.3 kJ/mol.…”

“…In later times, as some researchers emphatically claimed that there was no evidence for the direct roles of bicarbonate [9][10][11][12], the general opinion shifted against the "PS II-binding based effects" school of thought. In response, while a few of the original advocates toned down their support for bicarbonate being crucial [13], a few others have campaigned steadfastly for bicarbonate to play more direct roles [14][15][16]. In the context of the conundrum prevailing on bicarbonate (as well as several other additive molecules'/ions' ability to impact the photosynthetic process), we apply the murburn model of photosynthesis [17][18][19][20][21][22][23][24][25] to clarify upon several other associated facts from the literature and reason out the structure-function correlations of proteins and dynamics of molecular interactions in milieu.…”

Bicarbonate use and carbon dioxide concentrating mechanisms in photosynthetic organisms

“…Diversified modes of bicarbonate use are determined by the stoichiometric relationships among protons, electrons, and inorganic carbon. Proton and bicarbonate are the substrates of photosynthetic oxygen evolution (Wu 2021). Therefore, direct bicarbonate uptake including via anion exchanger and transporters, bicarbonate dehydration via external CA and P-type H ?…”

“…So far, it has not been found the bicarbonate can transport across the thylakoid membranes into the thylakoid lumen (Wang et al 2011). However, bicarbonate photolysis in thylakoid membranes provides protons, electrons, and carbon dioxide, which would concentrate and elevate the CO 2 concentration at the site of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) (Wu 2021). Therefore, even if there is no direct bicarbonate use dependent on CCMs in plasma membrane, the carbon dioxide from the atmosphere continuously enters the cell membrane due to great concentration difference, which resulted from the indirect removal of inorganic carbon within the plasma membrane via bicarbonate photolysis in thylakoid.…”

Quantification of Glucose Metabolism and Nitrogen Utilization in Two Brassicaceae Species under Bicarbonate and Variable Ammonium Soil Conditions

“…Moreover, bicarbonate photolysis and water photolysis could both be sources of photosynthetic oxygen [8,9]. This has resulted in a revised formula of photosynthetic oxygen evolution as follows: 2H 2 O + CO 2 → H 2 O + H + + HCO 3 − → O 2 + 4e − + 4H + + CO 2 [10], which should be sourced from both bicarbonate and water in a 1:1 (mol/mol) stoichiometric relationship [11]. Hence, it confirmed that bicarbonate significantly contributes to plant growth in karst habitats.…”