CARBON DIOXIDE EXCHANGE DURING THE SHORT INDUCTION PERIOD 1339 



Curves of a somewhat different type were obtained with wheat plants 

 at higher concentrations of carbon dioxide (0.07 to 0.24%; no higher con- 

 centrations were used). In these curves (c/. fig. 33.21B), the induction loss 

 is considerably smaller than in the curves of the first type (as well as in the 

 experiments used for the construction of the inset in figure 33.8). The 

 full rate is reached in less than 1 minute ; and a secondary depression oc- 

 curs between 1.5 and 2 minutes simultaneously with a second "burst" of 

 fluorescence. An extreme form of this type of induction curves (type II) is 

 illustrated by figure 33.22C', obtained with Chlorella grown and studied in 



12 3 4 

 TIME, min. 



After 16 mm. in dark 



12 3 4 

 TIME, min 



After 4 min. in dark 



12 3 4 

 TIME, min. 



After 1 min. in dark 



Fig. 33.10b. CO2 absorption by Stichococcus bacillaris at varying temperatures (after 

 Aufdemgarten 1939). 5000 lux, 0.32% CO2. 



normal air. Here, the total induction loss is normal; but the initial carbon 

 dioxide "gulp" is much more pronounced than in figures 33.21A and 

 33.22A, and the inflection is consequently replaced by a distinct peak 20-30 

 seconds after the beginning of illumination. Characteristic in these curves 

 is the parallel (rather than antiparallel) development of carbon dioxide 

 consumption and fluorescence. (The registration of fluorescence occurs 

 without a time lag; therefore the peak of fluorescence in figure 33.22C 

 coincides approximately in time with the peak of carbon dioxide consump- 

 tion, although the latter is registered 15 seconds later.) 



The induction curves of McAlister are closely paralleled by the curves 

 obtained by Aufdemgarten (1939). As described in chapter 25 (page 853), 

 Harder and Aufdemgarten (1938) developed a method of rapid carbon di- 

 oxide assay, based on measurement of thermal conductivity of the gas 



