Aug. is, 1914 
Oxidases in Potatoes 
387 
experiments already described in this paper were stored at room tem¬ 
perature from July 12 to September 3, 1913. During that time the 
tubers were lying on a table exposed to the light, and the temperature 
during the period fluctuated between 15 0 and 25 0 C. There were 36 
tubers, soft but sound, yielding 170 grams of sprouts; the 36 tubers from 
which the sprouts had been removed weighed 2,670 grams. Only 22 c. c. 
of juice were obtained from the sprouts in the usual way. This juice 
turned immediately to a chocolate-brown color. The oxidase activity 
of the juice of the sprouts toward seven of the reagents is given in Table V. 
The oxidase activity of the juice of the tubers toward all of the reagents 
is given in Table VI. 
Tabl,E V .—Oxidase activities of the juice of the sprouts from Green Mountain seed-potato 
tubers 
Oxidase activity expressed in units as measured in the oxidation of the 
reagents. 
Pyrocate- 
chol. 
Tyrosin. 
Phlorid- 
zin. 
Resorcin. 
Hydro- 
chinone. 
Guaiacol. 
Para- 
cresol. 
O. 562 
O. 296 
o -359 
°-°55 
0. 807 
0. 
°-495 
1 Teuco base of malachite green. 
OXIDASE activity of the juice of the tubers 
The method of procedure in the case of the potato tubers was the same 
as that used with the foliage. The tubers were freed from adhering soil 
by means of cold, running water and were wiped dry with a clean towel 
and ground up whole. It has been known for some time that the juice 
obtained from the layers of the potato tuber near the surface is more 
active than that from the inner portions. Notwithstanding this variation 
of oxidase activity in different parts of the tuber, the whole tubers, 
including the peel, were used for these experiments. This was done to 
avoid the introduction of new factors. The results are presented in 
Table VII. 
To see whether the oxidase content of the juice from the tubers bears 
any relation to either the age of the plant from which the tubers are 
derived or their own weight, the ratio of oxidase content to age and 
weight was represented graphically. In the figures 13 to 20 (see footnote, 
p. 379 ) two sets of curves are given. In both sets the oxidase activities of 
the juices are shown on the ordinates, while the ages and weights, respec¬ 
tively, are laid off on the abscissae. The curves formed by the continu¬ 
ous lines show the relation of age to oxidase content and the curves 
formed by the thin broken lines show the relation of the size of the 
tubers to their oxidase content. 
From these curves no definite relationship is apparent between the 
oxidase content of the tubers on the one hand and their age or size on 
