OXIDASES IN HEALTHY AND IN CURLY-DWARF 
POTATOES 
By H. H. Bunzel, 
Chemical Biologist , Plant Physiological and Fermentation Investigations , 
Bureau of Plant Industry 
INTRODUCTION s 
The curly-dwarf, among other related potato diseases, has been 
described very fully in one of the recent publications of this Department 
(Orton, 1914), 1 in which the very confusing literature on the subject of 
potato maladies referred to vaguely in the past as leaf-roll, curly-top, 
blight, Krauselkrankheit, Blattrollkrankheit, etc., is critically reviewed. 
On the basis of this review and of the work done by the Office of Cotton 
and Truck Diseases and Sugar-Beet Investigations, which has made a 
thorough survey of the principal potato districts on this continent, as 
well as abroad, a number of distinct diseases are recognized, each with 
its characteristic symptoms and probable cause. 
Some of these diseases, particularly the leaf-roll and the curly-dwarf, 
can not be traced to organisms of any sort for their origin and are sup¬ 
posedly disturbances of a purely physiological nature. To throw light on 
this matter, Mr. W. A. Orton, of the Bureau of Plant Industry, requested 
the writer to make a quantitative study of the oxidizing enzyms of 
potatoes at Houlton, Me., and immediate vicinity. Oxidase determina¬ 
tions were there carried out with healthy material, as well as with plants 
having the curly-dwarf disease. In this paper only such plants were 
considered to have curly-dwarf as showed the characteristic symptoms 
described by Orton (1914). 
This is not the first attempt to correlate enzymatic disturbances with 
plant diseases. Sorauer (1908) was the first one to attribute the leaf-roll 
of potatoes to disturbances in the oxidase mechanism of the tubers. 
According to this author, the dark patches observable on the cut surfaces 
of such tubers are due to a greater oxidase content than is found in normal 
tubers; the abnormalities of the foliage are due to malnutrition through 
the tubers. His conclusions are based on chemical experiments of Grtiss 
(1907). The most important and complete investigation of the subject 
was made by Doby (1911--12), who reached the very important conclu¬ 
sion that the oxidase content of the diseased tubers is greater than that 
of the normal ones. He also found a higher ash content and lower 
percentage of starch and insoluble protein in the diseased tubers, stating 
1 Bibliographic citations in parentheses refer to “literature cited," p. 403-404. 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
(373) 
Vol. II, No. 5 
Aug. 15, 1914 
G—30 
