The participation of phosphorus in biological oxidation-reduction reactions of the type found in glycolysis ADP {ne} PO{sub 4}H{sup -} + 3-phosphoglyceraldehyde + DPN{sup +} = 3-phosphoglycerate{sup -} + 2H{sup +} + DPHN + ATP has suggested theories in which similar reactions are proposed for photosynthesis. In these theories the reducing power of photosynthesis is utilized not only for reduction of carbon dioxide but also, by means of coupled oxidations, for the generation of high-energy phosphate bonds, or in the last reference directly for the generation of high-energy phosphate. Since in these theories acyl phosphate is formed from inorganic phosphate, they are amenable to proof without isolation of particular intermediates, by means of radioactive phosphorus. It would be expected that the rate of conversion of inorganic phosphate to organic phosphate would be greater in light than in the dark. They have investigated this possibility under a variety of conditions and are unable to substantiate the theories.