CARBON DIOXIDE EXCHANGE DURING THE SHORT INDUCTION PERIOD 13-41 



dioxide curves are differential rate curves. Furthermore, in figure 33.2, 

 the oxygen hberation is partly compensated by rapid oxygen consumption 

 by cathodic reduction. If these factors are kept in mind, and the carbon 

 dioxide curves are corrected for sluggishness, the similarity between the 

 course of the oxygen liberation and that of carbon dioxide consumption 

 becomes striking. It would be interesting to compare quantitatively not 

 only the timing of changes, but also the volumes of oxygen and carbon di- 

 oxide involved in them. In a rough measurement, Aufdemgarten (1939) 

 found no marked deviation of Qp from unity during the first 10 minutes of 

 illumination (19.5° C, 5000 lux, 0.6% CO2). 



Later, similar conclusions were reached and generalized by Warburg 

 and co-workers, as described above in section 2; but measurements by 



(a) 



{b) 



Fig. 33.11b. Time course of CO2 uptake in Stichococcus bacillaris after varying 

 periods of darkness (after Aufdemgarten 1939). 5000 lux, 1.0% CO2, 15 min. 

 dark, 4 min. light, 1 min. dark, 4 min. light, (a) Kolkwitz solution, 18.4° C; 

 (6) Eiler solution, 18.7° C. 



Emerson and co-workers, also reported there, revealed considerable minute- 

 to-minute variations in Qp, even in cases in which the time course of the 

 exchange of the two gases is cjUalitati vely the same ; extreme deviations of 

 Qp from unity occur when the oxygen burst is combined with a carbon di- 

 oxide burst (see below). 



The consumption of carbon dioxide during the gulp is independent of 

 the dark period (between 1 and 10 minutes; cf. fig. 33.10a) as well as of 

 temperature (between 13 and 25° C, cf. fig. 33.10b). This behavior is typi- 

 cal also of the fluorescence burst {cf. part B). The oxygen gush has not 

 been studied at different temperatures, but we may presume that it, too, is 

 unaffected by temperature. If this is true, these three phenomena must 

 be due to a straight photochemical reaction. On the other hand, the sub- 

 sequent inhibition, which dominates the short induction period, depends 

 on the length of the dark interval as well as on temperature, and must there- 

 fore be associated with thermal reactions, both in its preparation (deactiva- 

 tion) and in its liquidation (reactivation of the photosynthetic mechanism). 



In contradiction to other observers, Aufdemgarten found that the dura- 



