94 



BIOLOGICAL CHEMISTRY 



Even in spite of these corrections there is a slight decrease 

 in the temperature coefficient as the temperature rises, but 

 such a slight departure from a mathematical exactitude is 

 not unusual in many physico-chemical processes. 



The rate of photosynthesis depends upon the presence of 

 the above mentioned limiting factors. Thus the rate increases 

 as the carbon dioxide increases, until a certain concentration 

 is reached, when the photosynthesis remains uniform in rate, 

 even if the concentration of carbon dioxide is increased further. 

 By using jweaker light the maximum is reached with a lower 



FIG. 20. Relation of carbon assimilation to carbon dioxide supply, 

 temperature and illumination in Elodea. 



By following the horizontal lines the minimal carbon dioxide supply, temperature and 

 illumination can be found for any rate of carbon assimilation, or given the amount of carbon 

 dioxide supply, the temperature and the illumination, the carbon assimilation will be the lowest 

 value on the horizontal line opposite one of these factors. 



(From " Proc. Roy. Soc." F. F. Blackman.) 



concentration of carbon dioxide, and by increasing the 

 intensity of illumination the rate rises pari passu to a still 

 higher concentration of carbon dioxide. ! 



When the intensity of illumination is being tested a similar 

 inter-relation between it and the concentration of carbon 

 dioxide can be demonstrated.* 



* The amount of chlorophyll is never a limiting factor during the 

 developmental stage of the chlorophyll apparatus. A. A. Irving, 

 Ann. of Bot., 1910, vol. 24, p. 805. 



