"The combination potato-f. infestans was chosen as the object of this study because of the considerable amount of background information available on the physiology and biochemistry of both members of the pair and also because this combination represents an advanced type of parasitism, and the genetics of the pathogenicity is known. In brief, the main purpose of this work was to determine by means of histochemical tests the effect of f. infestans infection and the distribution and relative activity of succinic, malic and glucose-6-phosphate dehydrogenase in tubera of a resistant and a susceptible potato variety. These determinations were to be made at different stages of the disease, starting as early as possible after inoculation and using tuber pieces of different dimensions. Also a study of NAD and diaphorase concentration as limiting factors in the activity of these enzymes was carried out. Finally these enzymatic reactions of the host cell were correlated with those of the cells of the invading pathogen." --