Studies on Factors influencing the Changes of Hydrogen-ion Concentrations of Culture Solution and their Relation to the Mycelial Growth of Stagonospora carpathica

Abstract

(1) This paper deals with the results of experiments on the effect of autoclaving upon changes of pH value of culture solutions adjusted with acid and alkali and their relation to the mycelial growth of Stagonospora carpathica. The adjusted pH value of a modified Czapek-Dox medium changes also by leaving as it is without the fungus growth.
(2) The potato decoction with 2% glucose and a modified Czapek-Dox medium change their pH values by autoclaving. In the writer's experiment, all of the media showing alkaline reactions lower than pH 11 changed their pH values to about pH 5.8. The mycelial growth of Stagonospora carpathica, the causal fungus of the brown spot of broad bean, was tested in these media by inclubating for 10 days at ca. 26°C. The results show clearly that the higher the initial pH value before autoclaving is, the weaker the mycelium grows in dependentof the pH value after autoclaving. This fact is probably due to the decomposition of glucose in media.
(3) The pH values of the modified Czapek-Dox solutions in the alkali-side fall remarkably within 2 days, when they are left in the laboratory without planting of the fungus. Such falling in the pH value is probably due to the fact that the alkali in media absorbs carbon dioxide from the air.
(4) From the results of the above experiments, it may be concluded that, for the purpose to minimize or avoid such obstacles, the sugar- and the mineral salts solutions must be mixed aseptically, after they have been autoclaved, and the fungus is desirable to be transplanted on such medium as soon as possible.