Aug. is, 3914 
Oxidases in Potatoes 
397 
These curves seem to show no definite tendency such as was seen in 
the case of the growing leaves of healthy plants. This is to be expected 
when it is considered that the physiological condition of the plants and 
presumably the oxidase contents of the juices are here influenced by two 
factors combined, age and disease. Past experience has shown that the 
oxidase activity of the plant juices is markedly affected by physiological 
disturbances such as the curly-dwarf disease of potatoes seems to be. 
The magnitude of the effect on the oxidase activities probably depends 
on such factors as the age of the plant when the diesase first took hold, 
Fig. 20. —Curve showing oxidation of p-toluidin in the presence of the juice of potato tubers. 
the length of time elapsed since, the individual resistance of the plant, 
etc. None of the factors are susceptible of measurement; the plants ex¬ 
amined are influenced by them to different degrees and are therefore not 
comparable. 
However, they all showed the typical curly-dwarf symptoms, and if the 
oxidase activities of the leaf juice are influenced by the apparent physi¬ 
ological disturbances the influence should be noticeable by a deviation 
of the oxidase activities from the normal and in a definite direction. 
That such a deviation from the normal actually exists is indicated by 
the curves in figures 6 to 12 . With most of the reagents used the broken 
