lo6 BOTANICAL GAZETTE 



FEBRUARY 



The work was done in part at the Missouri State Fruit Experi- 

 ment Station and in part in the Botany Department of the Uni- 

 versity of Chicago. 



Historical 



The problem of oxidation by plant and animal tissues or tissue 

 extracts has been studied by many investigators since the time of 

 the pioneer work by Schonbein, the discoverer of ozone. An 

 immense literature has accumulated, for reviews of which the reader 

 is referred to publications by Clark (14), Kastle (24), Battelli 

 and Stern (5), and Atkins (3). In this paper only those articles 

 will be cited which bear directly on the problem in hand. 



That pathological conditions in plants are often accompanied 

 by increased oxidase activity has been shown repeatedly in recent 

 years. Woods (35) found greater oxidizing power in the chlorotic 

 portions of tobacco leaves affected with mosaic than in the green 

 portions; this has been confirmed by Allard (i) and by Frei- 

 berg (20). SoRAUER (31, 32) and Doby (17), working with leaf- 

 roll of potatoes, found oxidase activity greater in diseased tubers 

 than in healthy ones, although the former makes the point that 

 this greater enzyme activity is to be considered a symptom of the 

 disease rather than the cause. Bunzell (ii), working with the 

 curly-dwarf disease of potatoes, showed by an extensive series of 

 tests that ''affected plants have a greater oxidase activity than 

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

 in the juice of their fohage." Similar results were obtained by 

 Bunzell (id) in work with curly- top of sugar beets. All 4 of 

 these diseases are of the so-called physiological type, and the 

 question is still unsettled for the last 3 whether the increased 

 oxidase activity is the cause of the disease or merely the result of 

 disturbances due to the real but at present unknown cause. 



In the case of diseases whose cause is known the oxidase situa- 

 tion seems to be about the same as for those already mentioned. 

 Reed (29) found that the juice of apples affected with bitter rot 

 (Glomerella cingulata) has greater oxidase activity than that of 

 sound apples. In his previous work the writer (30) found that 

 diseased apple bark shows greater oxidase activity than healthy 

 bark, and is at the same time less acid. This seems to indicate 



