OXYGEN EXCHANGE DURING THE SHORT INDUCTION PERIOD 1331 



content affect the heat conductivity. By absorbing carbon dioxide chemi- 

 cally before the gas enters the "diaferometer," it becomes possible to meas- 

 ure the oxygen exchange alone. Van der Veen (1949^) demonstrated in 

 this way that in heat-pretreated algae the surviving carbon dioxide gulp 

 and gush (after exposure to light and darkness, respectively, cf. next sec- 

 tion) are unaccompanied by any oxygen exchange {cf. fig. 33.6E)— a sug- 

 gestive example of the independence of the exchange of carbon dioxide 

 from that of oxygen during the transient periods. 



The electrochemical data of Blinks and Skow, and of Damaschke et al, 

 can be compared with the results obtained by a similar method by Brackett 

 and co-workers. 



cS"! , ^ y N CO2 line 







cS'g 



.O2 line 



Time 

 Fig. 33.6E. CO2 gulp upon illumination (upward arrow) and burst upon dark- 

 ening (downward arrow), of heat-treated leaves of Holcus lanatus (after van der 

 Veen 1949^). No uptake or release of O2. Measured with a diaferometer. 



Olson and Brackett (1952) and Brackett, Olson and Crickard (1953 '-2) 

 studied the induction phenomena in Chlorella with a polarographic oxygen 

 meter that permitted readings every 10 seconds. They used dilute cell 

 suspensions, illuminated simultaneously from two sides; the uniformity of 

 illumination, achieved in this way, removed, according to their findings, 

 some adventitious features of the induction picture. 



Brackett, Olson and Crickard (19530 found that the respiration of 

 Chlorella underwent considerable changes in the first few minutes of dark- 

 ness after exposure to light. The typical picture of this respiration induc- 

 tion included a gulp of oxygen taking place in the first 10-20 seconds of 

 darkness (probably related to the burst observed by Damaschke et al, 

 but apparently smaller in volume), a minimum, a second, flatter maximum 

 reached in 1-4 minutes (probably related to the respiration peak noted 

 manometrically by Emerson et al), and a gradual decay to a steady level. 

 (These observations are to be discussed again under "Photosynthesis and 

 Respiration," section 3, Chapter 37, cf. figs. 37D.31 and 32.) During the 

 illumination period, Brackett et al assumed respiration to change smoothly 

 (and approximately logarithmically) from its level at the end of the pre- 



