ROLE OF RESPIRATION IN INDUCTION PHENOMENA 1427 



bursts of activity they noted in the first minute of both hght and darkness 

 (or "bright" and ''dim" hght) were revelations of steady high rate of gas 

 exchange in hght — the high rate of anabohc photoprocess being revealed 

 at the beginning of illumination, and the high rate of catabolic "anti- 

 photosynthesis" at the beginning of darkness (where it takes seconds or 

 minutes to be completed). We have concluded before that this interpreta- 

 tion is not in agreement with the totahty of experiments, and that the ob- 

 served bursts and gulps must be considered as transients rather than as 

 "tail ends" of steady metabohsms before the change in illumination. 

 Franck (1953) has attempted a quantitative analysis of the experiments 

 described in Warburg's papers to show that these transients can be explained 

 by assuming that respiration intermediates (of the reduction level of glyc- 

 eric acid), accumulated during the dark period, become available for photo- 

 chemical reduction in the first minute of illumination, and that this photo- 

 chemical half-way reversal of respiration requires only two quanta (per 

 one nonliberated molecule of CO2 and one nonconsumed molecule of oxy- 

 gen). Because of the importance of this question for the controversy 

 about the true minimum quantum requirement of photosynthesis, Franck's 

 calculations will be given in more detail in chapter 37D (section 4d) . 



The absence of induction losses in the Hill reaction of Chlorella cells 

 and isolated chloroplasts poses a question for the Franck-Gaffron theory of 

 induction. It appears offhand that the simplest explanation of this fact 

 would be to renounce the concept that the origin of the induction loss lies 

 on the "oxidation side" of the photochemical process proper (e. g., in the 

 inactivation of the oxygen-liberating enzyme), since processes there must 

 be the same in photosynthesis and in the Hill reaction, and to seek this ori- 

 gin on the "reduction side" of the primary photochemical process, where 

 the Hill reaction differs from photosynthesis. Franck suggested, however, 

 that this argument is not necessarily convincing, provided one attributes 

 the bulk of the induction loss to a "narcotization" of photochemical ap- 

 paratus by oxidation products formed in consequence of the accumulation 

 of photoperoxides when the oxygen-liberating enzyme is inhibited. These 

 "narcotics," he argued, may be unable to displace "substitute oxidants," 

 such as quinone, from their position as hydrogen acceptors in contact with 

 chlorophyll (and thus to inhibit temporarily the Hill reaction), while they 

 are able to prevent the access to chlorophyll of hydrogen acceptors (such 

 as phosphoglycerate) which must be reduced in photosynthesis. Although 

 this explanation is not implausible, it must be acknowledged that the at- 

 tribution of induction to the inhibition of the oxygen-hberating enzyme as 

 the primary cause rests on circumstantial evidence. It could perhaps be 

 revised without destroying the main ideas of Franck's induction theory, 

 which include the inactivation, in the first moment of illumination, of some 



