The reaction occurs in the light reactions in all photosynthetic organisms. A few organisms, including the alga Chlamydomonas reinhardtii and cyanobacteria, have evolved a second step in the dark reactions in which protons and electrons are reduced to form gas by specialized hydrogenases in the chloroplast.
the reaction occurs in the light reactions in all photosynthetic organisms a few organisms including the alga chlamydomonas reinhardtii and cyanobacteria have evolved a second step in the dark reactions in which protons and electrons are reduced to form gas by specialized hydrogenases in the chloroplast