12 DYNAMICS OF PHOTOSYNTHESIS 



We may now test this assumption by calculating the amount of 



photosynthesis which is to be expected after the lapse of a given time. 



According to the ordinary equation for a monomolecular reaction, 



C = A-Ae-^'^ 



in which T is time, c is the basis of natural logarithms, and K is the 

 velocity constant of the reaction. 



We may denote the amount of photosynthesis by P. If the rate 

 of photosynthesis is directly proportional to the amount of C, we may, 

 for convenience, put 



When the rate has become constant we find that a unit amount of 

 photosynthesis is produced in 20.4 minutes (average of the last 3 

 periods in Table I), hence the rate of photosynthesis at that time is 

 1 -r- 20.4 = 0.049. This is by assumption equal to C when A is 

 completely transformed into C and this is in turn equal to A at the 

 beginning of the reaction. Hence A at the start = 0.049. We may 

 substitute this value in the equation and find the value of K by trial. 

 If we put A' = 0.049 we get the values given in Table I. Better 

 agreement with the observed values is obtained by taking lower 

 values of K. This produces a gradual falling off in subsequent values, 

 but it is possible that this might actually occur if the experiment could 

 be continued for a sufficient length of time. 



The agreement between the observed and the calculated values is 

 very satisfactory except at the start. In this connection it may be 

 pointed out that at the beginning of a reaction disturbances are to be 

 expected. 



It is therefore e\adent that the assumption justifies itself by giving 

 an adequate quantitative explanation of the observed results. The 



