THE OXIDASES IN RELATION TO PLANT PATHOLOGY 299 



composition. It has been suggested by Bunzel that plants 

 with an excess of oxidase are in a condition of " fever." 

 It must, however, be borne in mind that BunzeFs deter- 

 minations are in reality measurements of the peroxide con- 

 stituent of the complete oxidase system, since they are 

 based upon the absorption of oxygen through the direct 

 action of the juice on pyrogallol without the addition of 

 hydrogen peroxide. Whether they really indicate differ- 

 ences in the absolute amount of enzyme, or are explicable 

 by variations in the amount of peroxide or even of inhibitor, 

 is undoubtedly of great interest, but must be considered as 

 being only of secondary importance as compared with the 

 fact that the absorption of oxygen is far greater in the 

 diseased and stunted plants than in the normal. 



OXIDASES IN HEALTHY AND CURLY-DWARF POTATOES. 



Under the above heading Bunzel (1914) has published 

 another elaborate comparative study of plant tissues, 

 normal and pathological. The plan of the investigation 

 was very similar to that on the beet, but a great variety 

 of oxidizable materials, eighteen in all, was employed. It 

 was found that the oxidase activity of the sap pressed from 

 the foliage of normally developing potato plants is greatest 

 in the early stages of development. It falls off with growth 

 of the plants, and rises again when growth has about 

 attained to its maximum. Curly-dwarf potatoes were 

 shown to possess a greater degree of oxidase activity than 

 healthy ones of the same age, both in the juice of tubers 

 and of foliage. The numerical results of the original paper 

 are clearly shown in graphs, but need not be considered in 

 detail here, as the method has already been sufficiently 

 illustrated. 



The significance of such changes in oxidase activity is 

 most probably due to the importance of this class of enzyme 



