CATALYSIS AND ENZYME ACTION 



61 



For a temperature interval of ten degrees the rate is doubled 



or trebled, for twenty degrees it is four or nine times as fast, 



and for thirty degrees eight and twenty-seven times as fast 



7* 



FIG. 13. Effect of temperature on rate of reaction (carbon assimila- 

 tion of cherry laurel leaf). 



The increase of rate is shown by the dotted line. This is calculated from the rate of 

 assimilation at 9 and 19 C., 3.8 and 8'o mg. respectively, a coefficient of n for ten degrees 

 Centigrade. 



The full lines show the falling off in assimilation with maintained temperatures of 30-5, 

 37' 5 and 4O'5 C. These are plotted with the baseline as representing times, so that exter- 

 polated to zero time the curves cut the dotted curve. This diagram illustrates the falling off 

 in {activity at higher temperatures due to the destructive action of high temperatures on 

 the tissues of the leaf. 



From "Annuls of Botany." F. F. Blackman. 



