Utilization of electron spin resonance spectroscopy for observation of in vivo response to fungicides

Electron spin resonance studies of the in vivo response to fungicides (chloranil and thiram) by Aspergillus niger of different ages are described. The spores possessed a natural free radical signal which grew rapidly upon application of chloranil. Thiram, on the other hand, produced weak changes in the free radical region but easily detectable changes at lower fields, indicating involvement of copper and iron. In addition, flow experiments are described in which the production and decay of the chloranil semiquinone radical produced in the reaction of solutions of chloranil with extracts of bakers' yeast were monitored, both in the absence and in the presence of several buffers and respiratory chain inhibitors.