OXYGEN EXCHANGE DURING THE SHORT INDUCTION PERIOD 



1325 



Warburg, Geleick and Briese (1951) studied dilute Chlorella suspensions, 

 illuminated with a red light beam, superimposed on white "background" 

 illumination just sufficiently to compensate steady respiration. These 

 "liright periods" of a few minutes duration alternated with similar periods 

 of illumination with the white "background" light alone ("dim periods"). 

 A very strong positive induction was noted at the beginning of both the 

 bright and the dim periods. A gradually subsiding "burst" of oxygen was 

 found in the first 1-2 minutes of "bright" illumination, and a gradually 



Fig. 3.3.6A. Splitting of photo- 

 synthesis into hght reaction and dark 

 hack-reaction at 20 °C. (two-vessel 

 measurements l>y Warl^urg, Geleick 

 and Briese 1951). 100 (A. cells per 

 vessel, compensating white back- 

 ground light; 546 ni/u light added for 

 first 3 minutes. 10.0% CO2. Pohits: 

 average of measurements at cor- 

 responding tim9s in 1(1 cycles. 



E 

 E 



3 - 



Net photosynthesis 

 y = 0.19 



3 I 



MINUTES 



subsiding "gulp" of oxygen in the first 1-2 minutes of "dim" illumination. 

 Fig. 33.6A shows this for a 3 minute light-3 minute dark cycle at 20° C. 

 With the type of manometers used in this work, the precision of single 

 minute-by-minute pressure change determinations was low; the points in 

 the figure were therefore obtained by averaging the changes in the corre- 

 sponding minutes of ten cycles. 



Warburg et al. interpreted the results of the type of those in figure 33.6A 

 (more specifically, the steep initial slopes of the "bright light" segments) 

 as evidence that oxygen liberation begins, after a few minutes of darkness, 

 with a quantum requirement as low as unity. The average ratio Qp 

 ( = A02/-AC02) calculated from the total gas exchange during ten three- 

 minute periods of bright light, was about 0.85; this was considered as 

 evidence that the burst was one of complete photosynthesis (for which the 

 theoretical ratio is Qp = 1.0). 



The average ratio Qp{= AO./ACO.), calculated from the total gas ex- 



