QUANTUM YIELD 



1963 



action" amounts simply to a partial or complete photochemical inhibition 

 or respiration (we could call this effect "photochemical antirespiration"). 



Three of Warburg's experiments challenged this interpretation. (/) 

 The experiment in which the rate of oxygen consumption by respiration 

 was found to be the same in hght and in the dark, if carbon dioxide was 



CHLOROPHYLL CONCENTRATION 



Fig. 37D.35. Quantum requirement of photosynthesis of Chlorella pyrenoidosa in 

 relation to variations in chlorophyll concentration in units, c, related to true concentra- 

 tion of chlorophylls inside the cells, [Chi],-, by the relation [CHl]i = c/8.5 (after Brackett 

 et at. 19532). The curves are logarithmic curves with hmits 6, 7 and 8, respectively. 



effectively removed by alkaU (p. 901); this could be taken as proof that 

 respiration intermediates cannot replace deficient carbon dioxide as sub- 

 strate of photochemical reduction. {2) The experiments in which the 

 quantum requirement of photosynthesis was found to be 4 or less, far above 

 the compensation point, over periods of the order of 30 min. or 1 hr. (fig. 

 37D.25) ; this could be taken as proof that the high quantum yield be- 

 longs to true photosynthesis and not to mere photochemical "anti-respira- 

 tion." (3) The separation of the "light process" from the "dark back- 



