INTERPRETATIONS OF THE CARBON DIOXIDE DEPENDENCE OF THE HILL REACTION
Heretofore Warburg's one-quantum theory of photosynthesis has seemed inconsistent with the existence of the Hill reaction. The one-quantum theory states that massive oxygen uptake and CO2 release are preconditions of photosynthetic oxygen production, yet isolated chloroplasts produce oxygen at high rates apparently without consuming any oxygen or producing any CO2. Warburg has attempted to resolve the dilemma by pointing out a CO2 dependence of the Hill reaction. On the basis of this observation he proposed a reinterpretation of the Hill reaction which is consistent with the one-quantum theory. The effect of CO2 on isolated chloroplasts has been confirmed and some of the conditions which are necessary for the demonstration of the effect have been defined. It is not clear if CO2 is actually metabolized as Warburg claims. Contrary to Warburg's model, its participation seems to be at a site remote from the photochemical act. A number of other reasons for doubting the reality of the one-quantum mechanism are presented.