INFLUENCE OF REACTION ON GERMINATION 229 



TABLE 22 



Time (Hours) Required for Germination of Spores at Different 



Temperatures 



1 Failed to germinate. 



INFLUENCE OF REACTION ON GERMINATION 



The pH which limits germination has been determined for many 

 species of fungi. A divergence of opinion exists concerning the 

 proper appraisal of the value of such knowledge. No such dis- 

 agreement exists, however, regarding; the usefulness of data in- 

 volving the influence of reaction on mycelial development of 

 fungi in cultures or in soil and other natural habitats. 



Most fungi germinate and develop best in acid media. The kind 

 of nutrient, however, exerts a profound influence upon the re- 

 sponse to the reaction of the medium. Webb (1921) made. a 

 comparative study of the effects of hydrogen- and hydroxyl-ion 

 concentration upon the germination of B'otrytis cinerea, Asper- 

 gillus niger, Penicillium italicum, P. cyclopium, Lenzites saepiaria, 

 Puccinia graminis, Fusarium sp., and Colletotrichum gossypii in 

 four liquid media, namely, solutions of mannite and of peptone, 

 Czapek's nutrient, and sugar-beet decoction. All except Fusarium 

 sp. and C. gossypii responded favorably to successively increasing 

 concentrations of hydrogen ions in all media within the range pH 



7.0 to 3.0-4.0. Colletotrichum gossypii responded best within the 

 alkaline range. Specificity of response in each nutrient is illus- 

 trated by the fact that Botrytis cinerea germinated in mannite 

 from pH 1.6 to 6.9, but did best at pH 3.0; in Czapek's nutrient 

 from pH 2.5 to 9.6, but best at pH 3.0 to 3.6; in peptone from pH 



2.1 to 8.7, but best at pH 4.0 to 5.3; and in beet decoction from 

 pH 2.0 to 9.8, but best at pH 4.0 to 7.0. 



Similar studies on other organisms show that pH 6.86 is opti- 

 mum for germination of Urocystis occulta, with no germination 



