INFLUENCE OF OXYGEN ON INDUCTION 1367 



Franck, Pringsheim and Lad (1945) found much less pronounced effects 

 of alkali and quinone on anaerobic inhibition than Noack, Pirson and 

 Michels. Franck attributed this difference to the use of streaming gas 

 which kept the local oxygen concentration safely below the "reactivation" 

 level even in alkaline medium. Noack's experiments, on the other hand, 

 were made in a closed system, where even partial removal or neutralization 

 of the inhibiting material may have been decisive in determining the balance 

 between oxygen accumulation by residual photosynthesis and oxygen con- 

 sumption by side reactions not contributing to the reactivation of photo- 

 synthesis. 



According to Franck and co-workers, an important factor determining 

 the extent of inhibition of a cell culture by anaerobic incubation is, beside 

 duration of the incubation period (the difference between the results of 

 Franck and of Noack may have been due, in part, to the latter's using a 

 thirteen hour incubation period and the former, a three to five hour incuba- 

 tion period), the concentration of the algae in the suspension. This indi- 

 cates that inhibition is caused by a product capable of diffusing into and out 

 of the cells. Since young cultures, placed in suspension media that previ- 

 ously contained old, anaerobically incubated algae, often show only Uttle 

 deterioration, one of the effects of anaerobic incubation (to which old cul- 

 tures appear to be more sensitive) may be a change in the permeabiUty of 

 the cells for general, "narcotic" poisons. 



It is obvious from the above that the induction curves observed after 

 anaerobic incubation must depend on the balance of residual photosynthesis 

 and various competing, oxygen-consuming processes and may therefore dis- 

 play a great variety of shapes. This applies to the course of photosynthesis 

 in the first minutes (or hours) after the beginning of illumination; the 

 phenomena in the first few seconds of exposure, on the other hand (best 

 revealed by the observations of fluorescence), are simpler under anaero- 

 bic than under aerobic conditions. In general, anaerobic pretreatment 

 makes the fluorescence start at a high level immediately upon illumination, 

 thus eliminating all or most of the usual "fluorescence burst" (cf. fig. 

 33.47). Photosynthesis, on the other hand, begins under anaerobic con- 

 ditions, at a low level (i. e., the initial oxygen burst and carbon dioxide 

 gulp probably are absent). It looks as if, in this case, the inhibiting action 

 is fully developed in the dark, and requires no initiating photochemical re- 

 action. Emerson and Lewis (1941) found that the photochemical carbon 

 dioxide gush, too, is absent in Chlorella after anaerobic incubation. 



As mentioned in sect. 2, the polarographic oxygen liberation curves 

 of Blinks and Skow (fig. 33.2), even if they were obtained after exhaustion 

 of oxygen in the layer between leaf and electrode, cannot be considered 

 characteristic of anaerobic conditions. McAlister and Myers (1940) ob- 



