EFFECT OF PREPARATORY REACTIONS ON LIGHT CURVES 1017 



posed by the deficiency of a finishing catalyst, Eb) is lower, the two may 

 be not too far apart. Therefore, in the narcotized state, when a large 

 fraction of the chlorophyll complexes is blanketed by the narcotic and 

 therefore inactive, the saturation level due to chlorophyll can become lower 

 than that due to the catalyst Eb- This will cause photosynthesis to be in- 

 hibited by narcotics even in strong light ; however, the per cent inhibition 

 will be smaller than in weak light. (This prediction is in agreement with 

 Wassink's findings on purple bacteria, but not mth his observations on 

 diatoms.) 



(c) Analytical Formulation: Effect of Preparatory Dark Reactions 



In chapter 27, a rather extensive effort was made to derive equations 

 for the function P = /[CO2] under different assumptions concerning the 

 preparatory dark reactions on the "reduction side" of the primary photo- 

 chemical process. The influence of light intensity was expressed in these 

 derivations {cf. equation 27.6) by assuming that the rate is proportional to 

 the concentration of the reduction substrate, [ACO2], and that the pro- 

 portionality factor, k*, is a function of the light intensity, /. The resulting 

 equations for P were then applied to the analysis of the carbon dioxide 

 curves, by assuming constant values of the parameter / {i. e., of fc^)- The 

 same equations can, however, equally well be considered as analytical ex- 

 pressions of the light curves, P = f{I), with [CO2] as parameter. A speci- 

 fic assumption must be made in this case concerning the relation of k* to 

 I (e. g., by postulating that /:* is proportional to /, k* = k*I, cf. eq. 28.13). 



The simplest equation for P in chapter 27 was equation (27.8). It was 

 based on the assumption of a dissociable carbon dioxide-acceptor complex 

 with no limitations on the rate of its formation. The corresponding light 

 cui'ves are linear (at least, if k* = k*I), and show no saturation effects. 

 (This is, of course, due to the fact that, in the derivation of equation 27.8, 

 the equilibrium concentration of the compound [ACO2] was supposed to 

 be undisturbed even by intense photosynthesis.) The equation of these 

 straight lines is (using k* as independent variable) : 



(28.1) P = {nk*K,P^,{CO^])/{l + K.[CO,]) 



Their slope is proportional to [CO2] at low carbon dioxide concentrations 

 and approaches a maximum at high carbon dioxide concentrations : 



(28.2) (rfPM-*)max. = nAo 



As soon as the assumption is made tliat the stationary concentration 

 [ACO2] is affected by the rate of consumption of this complex by photo- 

 synthesis {i. e., that the formation of ACO2 is not infinitely fast), the light 



