52 



PHOTOSYNTHESIS 



this type was suggested by Warburg in 19 19 and considered 

 later in more detail by G. E. Briggs (1935). 



Temperature. Investigations on the effect of temperature 

 on the rate of photosynthesis provide further evidence for a 

 mechanism of this type. As pointed out by Blackman the 

 maximum rate of photosynthesis at any temperature will 

 only be attained when the concentration of carbon dioxide 

 and the light intensity are both high. Under these conditions 



O 

 O 



h/gh light 



-*' 



low light 



\\\\\\\\\\\\\ 



12 



24- 



FIG. 



16 20 



Temperature ° C 



4.6. Effect of temperature upon rate of photosynthesis at high 

 (upper) and low (lower) hght intensities in Hormidium. (After 

 van der Honert.) 



Miss Mathaei (1904) found with leaves of cherry laurel and 

 of Helianthus a temperature coefficient of the order of 2-1 

 between 20° and 40° C. Above this temperature the rate of 

 photosynthesis began to decrease due, it was suggested, to 

 a progressive destruction of the photosynthetic mechanism. 

 This decline is thought to commence at temperatures above 

 about 28° C. and to dominate over the accelerating effect of 

 increase in temperature at temperatures above 40^ C. The 



