The number of protons, electrons and quanta of light involved to release two molecules of oxygen in C3 plants are respectively:

H2O→ 4H++ O2 + 4e-When one molecule of oxygen is released 4H+ and 4e- are involved. Therefore, to release two molecules of oxygen in C3plants 8 protons and 8 electrons are required.The number of light Quanta or photons required for the evolution of 1 mol. of O2 in photosynthesis is 8. Therefore, for production of two molecules of oxygen the number of light quanta involved is 8 X 2 = 16