1414 



INDUCTION PHENOMENA 



CHAP. 33 



taken as indication that the concentration of the free acceptor, [A], has 

 undergone an increase at the beginning of the light period. The influence 

 of this change on induction depends on whether the rate of carboxylation 

 was determined by the concentrations [CO2] and [A], or by the available 

 quantity of the carboxylating catalyst, Ea- It further makes a difference 

 if the steady rate of photosynthesis depends on the quantity of A -002 



Dork 



Light 



Dork 



-ACO^ 



-ACQ, 



^^^ 



^^^ 



Fig. 33.49. Induction effects that may be caused by CO2 acceptor, A; XL = induc- 

 tion loss; PU = pick-up. (a) Saturation light (saturation imposed by factors inde- 

 pendent of CO2 availability, e. g., by Eb limitation), (b) Transitional part of light 

 curve, [CO2] has effect on rate (Ea deficiency, e. g., in consequence of cyanide poi- 

 soning). 



complexes available for reduction, or is so strongly limited by other cata- 

 lytic factors (such as the availabiUty of the finishing catalyst, Eb), to be 

 practically insensitive to a depletion of the reduction substrate. 



Let us assume, as an example, that the latter is the case; furthermore, 

 that the concentration of carbon dioxide is high enough to saturate the ac- 

 ceptor in the dark and that the rate of carboxylation is proportional to the 

 momentary concentration of the free acceptor, [A]. In this case, the rate 

 of oxygen liberation will be constant throughout the induction period (since 

 according to our assumption a decrease in A -002 cannot affect this rate). 

 The initial rate of the carbon dioxide absorption, on the other hand, wdll be 

 low; it will gradually increase and the steady rate reached when [A] be- 



