452 



D, D. HENDLEY 



Space permits a discussion of only two of the induction effects il- 

 lustrated in Fig. 1, the acid gush and the initial uptake. Effects 

 similar to these have been studied in green plants and I shall try to 

 make a brief comparison. 



The acid gush. Blinks and Skow (3) were the first to observe an 

 initial pH decrease upon illumination in suspensions of the alga 

 Stephanoptera and at the surface of leaves of higher plants. Emerson 

 and Lewis (4) later published a detailed manometric study of an 

 initial "CO2 gush" from suspensions of Chlorella in acid phosphate 

 solution. 



12 3 

 MINUTES 



Fig. 2. 



Like the acid gush of the bacteria, the CO2 gush described by 

 Emerson and Lewis is, up to a point, larger the longer the dark 

 period preceding the illumination. After long dark periods both 

 gushes may reach the equivalent of 0.2 volume of CO2 per volume of 

 cells. 



The bacterial gush is usually followed in the light by a roughly 

 equivalent uptake of acid ("72" in Fig. 1) clearly distinct from steady- 

 state photoreduction. This rev^ersal of the acid gush in the light has 

 not been reported for the gush in algae, where the reaction is either 

 absent or so sluggish that it cannot be distinguished from photosyn- 

 thesis. 



On the other hand, both the bacterial and algal gushes are reversed 

 in the dark if the light is turned off during the gush. This may be 

 seen in Fig. 2, which shows the pH changes in a bacterial suspension 

 which was illuminated three times, the light being turned off when 

 the acid gush reached its maximum deflection. Each time the pH 

 was rapidly restored in the dark. The acid gush and the imniediatel}^ 



