Combined effect of bicarbonate and water in photosynthetic oxygen evolution and carbon neutrality

Carbon neutrality is widely concerned and highly valued by many countries. Biosphere has always maintained the balance between oxidized organic substances and assimilated organic matter, resulting in net-zero carbon dioxide (CO2) emissions and maintaining its own carbon neutrality. Nature has set a good example for human beings to coordinate oxygen (O-2) balance and CO2 balance, and achieve carbon neutrality. How does photosynthetic oxygen evolution initiate carbon and water neutrality? My synthesis shows that photosystem II functions as carbonic anhydrase to catalyze the reaction of CO2 hydration under physiological conditions, and CO2 hydration coupled with chemical equilibrium, H++HCO3--> 1/2 O-2 + 2e(-)+2 H++CO2, occurs in a photosystem II core-complex. Meanwhile, I focused on the revisiting of four classical heavy oxygen (O-18) labeling experiments and found that bicarbonate can promote photosynthetic oxygen evolution, and that photosynthetic oxygen evolution can alternately come from bicarbonate and water, not only water. Bicarbonate photolysis and water photolysis account for half of the photosynthetic oxygen evolution respectively, which can well explain the bicarbonate effect, Dole effect and plants' environmental adaptability. Photosynthetic oxygen evolution initiated the journey of water metabolism and carbon metabolism in nature, which led to the coupling as 1:1 (mol/mol) stoichiometric relationship between the reduction of CO2 and oxidation of organic carbon, coordinated the evolution of the atmosphere, hydrosphere, lithosphere and biosphere, and realized carbon neutrality in the whole Earth system.

Automated summary

Carbon neutrality is a widely concerned and highly valued issue for many countries. The biosphere provides a good example for human beings to achieve carbon neutrality by balancing oxygen and CO2. Photosystem II acts as a carbonic anhydrase in the process of photosynthetic oxygen evolution, initiating the carbon and water neutrality. The study also found that bicarbonate can promote photosynthetic oxygen evolution, and that photosynthetic oxygen evolution can come from both bicarbonate and water. This research sheds light on the understanding of photosynthesis and its role in achieving carbon neutrality in nature.