Abstract
Utilization of inorganic nitrogen for the timothy leaf spot fungus, Cladosporium phlei de Vries, was examined in this study. When the fungus was cultured in glucoseammonium nitrate medium supplemented with thiamine and pyridoxine, the pH in the medium lowered gradually during the first 17 days and thereafter rose. A similar experiment was conducted using the medium excluding any vitamin and essentially the same result was obtained. The lowering and rising of pH at the early and later stages were explained in terms of preferential utilization of ammonium ion prior to active utilization of nitrate ion.
