THE ENERGETICS OF PHOTOSYNTHESIS 



91 



Hence, without the back reaction 



dx 

 dt 



= I 



If the back reaction is regarded as a monomolecular reaction 



dx 



dt 



= I — kc 



(30) 



k beino; the velocity constant. In considering the concentration r, we find 



'dt 



fi — kc 



or after integration 



Substituting" c in equation 30 



^ = f<' 



,-kt\ 



or after integration 



J^.-yv(i-.-) 



X = i{l - f)t+\ (1 - e-'') 



If/ = 0, it follows from equations 31, 32 and 33 that 



c = 

 dx 



dt 



and 



For high values of /.: we find 



= 





dx 

 It 



= (1 - /)'• 



(1 - m + 



fi 



:3i) 



(32) 



(33) 



(34) 



Thus, equation 34 is valid for the steady state. The value off, i.e. the amount 

 of Oo reacting back at given values of/ and /, is determined by /: when the 

 measured light is removed. According to equations 31 and 34, the time / in 

 which the steady value f, is attained is determined by the factor {\ — < ). 

 It follows from these equations that 



c = c,(l - ^-*0 



