434 



H. GAFFKON 



Such compensation effects are particularly extensive after long dark 

 periods but tend to become shorter in repeated sequences of light and 

 dark. In Fig. 4 the first of the compensation effects is always longer 

 than the second. What completely erroneous results one would obtain 



Fig. 4. Dependence of length of compensation period on length of preceding 

 aerobic dark time. Upper curve: Recording showing a long compensation period 

 after 2 hours dark time, a short one after only 2 minutes dark time. Low rate of 

 photosynthesis. Lower curves: Rates of carbon dioxide uptake during the first 

 illumination period after several hours of darkness (I), and during the second, 

 following a dark time of about 4 minutes (II). In I the compensation lasts 1 minute 

 the entire induction period over 4 minutes. In II the compensation is shortened to 

 25 seconds, the induction period to 90 seconds. 



Fig. 5. Transitions dark-light in Chlorella after a series of 2-minute intermitten- 

 cies; 0.6% cell volume in 0.002 71/ bicarbonate. Upper curve at pH 8.5, lower 

 curve at pH 7.7. 



