CARBON DIOXIDE EXCHANGE DURING THE SHORT INDUCTION PERIOD 1343 



strong decline of the inhibition effect as a whole makes the gulp unobserv- 



able. 



The experiments described so far in this section indicated, in general, a 

 parallehsm between the course of induction as measured by carbon dioxide 

 uptake, and the time course of oxygen liberation, as described in the first 

 part of section 2, although, with the oxygen and carbon dioxide experiments 

 performed by different observers and on different objects, only qualitative 

 analogy can be asserted. Later in section 2 we reported more recent in- 

 vestigations, indicating the occurrence of "positive induction" (oxygen 

 gush) in the first minute of illumination ; we recall that Warburg and co- 

 workers assumed that the same applies also to carbon dioxide consumption 

 ("CO2 gulp"), but that Emerson and co-workers found this to be only oc- 

 casionally correct (e. g., in the first minute of illumination in fig. 33. 6D); 

 in other cases the oxygen gush was not accompanied by an equivalent car- 

 bon dioxide gulp. We will now discuss experiments on the course of carbon 

 dioxide uptake, which revealed strong "unilateral" carbon dioxide induc- 

 tion effects, not paralleled by similar changes in oxygen evolution. 



(The discussion of some two-vessel manometric induction measurements 

 in section 2, and of others in the present section is arbitrary, since all such 

 measurements give both AO2 and ACO2; it is justified by the greater em- 

 phasis laid in Emerson and Lewis's work on the "carbon dioxide burst," 

 and in Warburg's work on the "oxygen burst.") 



Strong deviations of the photosynthetic quotient from unity during the 

 induction period were first noted by Kostychev (1921). He found that, 

 in the initial 5 or 10 minutes of illumination of leaves or algae in an atmos- 

 phere containing 6% carbon dioxide, — ACO2 strongly exceeded AO2 (Qp = 

 0.21 — 0.79). According to Kostychev, the excess carbon dioxide absorbed 

 in the first minutes of illumination is compensated by a reduced uptake 

 later, so that the average value of Qp becomes unity after 15 or 20 minutes 

 illumination. 



Blinks and Skow (1938) and Emerson and Lewis (1941) observed, in 

 contrast to Kostychev, an initial deficiency of consum'ption (or even a 

 liberation) of carbon dioxide, not compensated by a slower evolution (or 

 outright consumption) of oxygen ; this means Qp values either > 1 or neg- 

 ative. 



Blinks and Skow (1938^ used a rapid potentiometric method for the 

 determination of the carbon dioxide exchange. They measured ACO2 by 

 means of a glass electrode immersed in the algal suspension, or pressed 

 against the surface of a leaf (c/. chapter 25, page 853). The evolution of 

 carbon dioxide revealed itself by a decrease, and its consumption by an in- 

 crease in pH. (Of course, similar effects could also be caused by formation 

 or consumption of other acids.) The response was so rapid that light 



