156 EFFECTS OF REACTION OF SUBSTRATE ON FUNGI 



such as reproduction, respiration, and enzyme production. In 

 general, these studies have been concerned with establishing the 

 range of pH within which growth can be accomplished. All 

 show that optimum growth occurs if the media are acid, and there 

 is abundant evidence to indicate that the range of pH that will 

 permit growth varies with the species, with the composition and 



100 



75 - 



£ 50 

 m 

 S 



>> 



S 





£ 25 - 







5 6 



Reaction of medium (pH ) 



8 



Fig. 23. Growth of certain Basidiomycetes in Richards' solution adjusted 

 to different initial degrees of aciditv. Cultures maintained at 25° C. (After 



Wolpert.) 



the initial reaction of the culture medium, and with temperature. 

 Representative results of the influence of reaction upon growth 

 of fungi are assembled in Table 12. 



The most significant feature indicated by Table 1 2 is that essen- 

 tially all the region of pH permitting growth lies within the acid 

 range. As a secondary feature it is apparent that each species 

 may differ in the limits of this range. It should be indicated that 

 the optimum pH does not occur at the midpoint. The under- 

 lying reasons for these facts seem to rest upon the isoelectric points 

 of the constituent proteins of the different species, as shown by 

 Robbins (1924). In Rhizopus nigricans and Fiisarinm ly coper sici 



