OXYGEN EXCHANGE DURING THE SHORT INDUCTION PERIf)D 1333 



Figure 33. 6F, taken from the second paper (1953-) of the same authors, 

 shows typical oxygen induction curves in three successive three minute 

 light periods, interrupted by nine minute dark periods. The circles repre- 

 sent luicorrected rates, the crosses, rates corrected for interpolated respira- 

 tion (dotted lines below). After thorough dark adaptation, the initial rate 

 of oxygen lil)eration in light may be zero (or almost zero, cf. the conclusions 

 of Franck ct al. in section G), and induction may cover up to 3 minutes, as 

 in the first segment of figure 33. OF. The initial rate becomes higher, and 

 the induction loss declines, in repeated cycles. The induction loss of oxy- 

 gen production appears complementary to Emerson and Lewis's carbon 

 dioxide burst (cf. below section 3) ; in fact, it can be accounted for approxi- 

 mately by assuming that, for each cjuantum of light diverted from the pro- 

 duction of oxygen, one molecule of carbon dioxide is liberated. 



In these experiments, too, there is no sign of an initial burst of oxygen 

 in light ("positive" induction, interpreted by Warburg and co-workers as 

 evidence of a "one-quantum process of photosynthesis"). It seems cer- 

 tain from Blinks' and Damaschke's polarographic measurements, however, 

 as well as from Emerson's more recent manometric results, that such a 

 burst does occur in some cases; however, its occurrence does not seem to 

 have the generality (and therefore probably, also, the significance) at- 

 tributed to it by Warburg, Burk and co-workers. 



Brackett, Olson and Crickard (1953^) observed a second, shallow mini- 

 mum of oxygen liberation on some of their induction curves (about 1 

 minute after the beginning of illumination). This, too, reminds one of the 

 shape of Emerson and Lewis's carbon dioxide burst (as well as of that of 

 Aufdemgarten's and van der Veen's carbon dioxide gulp, both of which 

 show two or more successive waves, cf. section 3). 



Brackett et al. plotted the oxygen liberation rate during the induction 

 period (after complete dark adaptation) on a log (Po/P) = f{t) scale, and 

 found that different runs showed different deviations from the logarithmic 

 approach to the steady rate — curvatures, breaks in slope, etc., seemingly 

 indicating complexity and variability even of the "normal" negative oxygen 

 induction. 



The most significant evidence concerning Warburg's hypothesis of oxy- 

 gen burst as evidence of strongly enhanced respiration in light was pro- 

 vided by isotopic tracer studies of Brown and co-workers. 



Brown (1953) measured respiration during illumination, independently 

 from photosynthesis, by using 0(18)-enriched oxygen {cf. chapter 37D, 

 section 3). He found, with ChloreJla, either no change in respiration rate 

 at all, or a sudden increase in respiration at the end of the illumination period. 

 If this result were generally valid, it would make Brackett's method of inter- 

 polation of respiration in light (figs. 33. 6F and 37D.32) inexact, affecting 



