1042 THE LIGHT FACTOR. I. INTENSITY CHAP. 28 



{HCO2}, is removed practically instantaneously, but that the oxidation 

 product, {OH}, has to undergo an enzymatic transformation (28.47Fb, c), 

 which includes a "bottleneck" reaction imposing an absolute ceiling 

 (28.47H) on the over-all rate of photosynthesis. 



If reaction (28.47Fa) runs too fast for the reactions (28.47Fb,c) to re- 

 move the oxidation products immediately, the "narcotization" mechanism 

 (28.47Fd, e) comes into play; accumulated {OH} reacts with ametaboHte, 

 H2M (supposed to be present in excess in the cells), and oxidizes it to a 

 "narcotic," HM, which is adsorbed on chlorophyll and inactivates it 

 (supposedly without affecting the absorption spectrum, but increasing the 

 yield of fluorescence). The narcotization is removed by reaction (28.47Fe), 

 which completes the oxidation of the "half-oxidized" product. (At a con- 

 stant concentration of oxygen, this reaction can be treated as monomolecu- 

 lar.) 



The rate of photosynthesis is, in this scheme, equal to the rate of the 

 limiting reaction (28.47Fc) : 



(28.47G) P = »^e[EOH] 



the maximum possible rate is (the subscript max. being justified by the 

 above-made assumption of practically instantaneous supply of carbon 

 dioxide) 



(28.47H) PZl: = nkeEo 



The factor n designates, as before, the number of elementary photo- 

 chemical steps of type (28.47Fa) required for the production of one molecule 

 of oxygen. 



We introduce the abbreviation: 



(28.47Ha) k = ^ 



An equation for the rate of photosynthesis can be obtained by deter- 

 mining the photostationary concentration [EOH] and then applying 

 equation (28.47G). The result is: 



(28.471) - - 2(fc - 1) 



Lv 2(fc - 1) ) k-i \ 



(One can easily ascertain that this equation gives correctly, P = for / = 

 0, and P'"^'^- = nA-eEo for 7 = oo .) 



The light curves (28.471) are nonrectangular hyperbolae with the initial 

 slope: 



nkji* nkjcnk* 



(28.47J) 



\dl Ji = o 



kekEo + k:Ch\o kUko + knCUo) 



