397 



T. T. Bannister and M. J. Vrooman 



Fig. 3. E(p , p ) and D(p , p ). Predicted by spill- 

 over model (a = 0.2, b = O.65; and separate package 

 model (a = 0.29, "b = 0.57). Everywhere to the left of 

 the contour E = 2.5, E maintains its maximum value of 



2.5 



Discontinuity of Derived Function . One discrepsJicy is the 

 discontinuity of the predicted E euid D functions along the 

 contour line E = 2.5. In the spill-over model, this discontinuity 

 reflects the assiamption that, with p-L smaller than balancing, 

 short-wave quanta are divided in the ratio b/(l-b) between the 

 two photoreactions, while with p-, greater than balancing, the 

 short-wave quanta in excess of those needed to reach the balance 

 are divided equally between the reactions. To remove this dis- 

 continuity, one could assume that the ratio of division of short- 

 wave quanta cheunges in a continuous fashion as Pj^/Pp increases. 

 Offhand, such a dependence would seem a conceivable property of 

 an energy- transfer mechanism. 



For the separate package hypothesis, the discontinuity is more 

 difficult to explain, since, in this case, b and a represent 

 simply the fixed fractions of absorption by the two separate 

 pigment systems. Possibly, a plausible explanation could be 

 found in terms of the kinetics of dark reactions associated with 

 the photoreactions. 



Saturation Effect . One notes a second discrepancy in that, 

 whereas the contours of E of the derived function are everywhere 

 straight lines radiating from the origin, the contours of the 

 experimental function are straight only for low p-j_ and pg, and, 

 for higher p, and pp, curve away in a counterclockwise sense. 



