Physiologie, 507 



The differences existing between the oxidase activity of the 

 healthy and of the diseased material are generally marked and the 

 greater activity is in the curl3'-dwarf potato phmts. The comparison 

 of the data for the healthy and curly-dwarf shoots shows thatamong 

 the 18 reagents onl\- three are oxidized raore readily in the pre- 

 sence of the juice of the healthy plants. Comparison of the leaves 

 of the two types of plants shows 7 of the 18 reagents to be more 

 readily oxidized by the health}^ juice; in the case of the two tj^pes 

 of tubers only two of the reagents showed greater oxidation by the 

 healthy material. Among 54 sets compared, 12 showed a greater 

 activity in the case of the healthy material, while the remainder, 

 42, showed a much greater activity in the case of the diseased plants. 



It seems safe to conclude that in general the oxidizing power 

 in the juices of the curly-dwarf potato plants is greater than in 

 those of healthy plants. The writer does not know as yet exactly 

 w^hat bearing, if any, the oxidases measured by him have on the 

 oxidation processes going on in the cells. A priori, one would con- 

 clude that the intensit}" of oxidation processes in the cells would 

 among other factors depend on the concentration of the various 

 oxidases present. If this were the case, one would expect cell respi- 

 ration to be more intense in the cells of the curly-dwarf tubers. The 

 diseased plants would be in a condition corresponding to "fever" 

 in animals. 



These results agree in their general nature with those obtained 

 in the case of the curl3'-top of sugar beets and the leaf-roll of pota- 

 toes. In all three cases an increase in oxidases and a general retar- 

 dation of growth are found. It w^ould be extremely interesting, 

 especially to plant physiologists, to find out what the rate of respi- 

 ration is in such dwarfed, presumabh^ "feverish" plants. Experi- 

 ments intended to throw light on this point are alread}^ being plan- 

 ned in the laboratory of the Office of Plant Phj'siological and 

 Fermentation Investigations. 



There are a number of facts brought out in this investigation 

 which open doors to new aspects of the physiology of development. 

 There seems to be a cycle in the activity of the expressed juice of 

 the foliage of normally developing potato plants. The juice of the 

 foliage of very young plants is more active than that of plants of 

 the same variety 40 or 50 days older After that stage of develop- 

 ment the activity rises again with increasing age. Quite in harmony 

 with these findings is the fact that sprouts of artificially sprouted 

 tubers of the same variety are much more active than the youngest 

 foliage examined. 



There seems to be a parallelism, therefore, between the inten- 

 sit}^ of physiological activit}- and the quantity of oxidases present. 

 This belief is strongh' corroborated b}' the fact that the physiolo- 

 gicaliy more active portions of the plant, such as the leaves, fur- 

 nish Juices with greater activity than the obviously less active 

 portions of the same plant, such as the stems. This has been found 

 by the writer not onlj' in the case of potato plants, but also in 

 sugar beets. 



In this connection the results obtained by Nicolas are very 

 interesting. He studied the respiration of individual parts of plants 

 and found that those organs which carry out the assimilating func- 

 tions of the plant showl;he greatest respiratory activity. The limbs 

 of the Organs which replace them in function, such as the phyllodia 

 and cladodia, have 1.4 to 4.5 times as great a respirator}' activity 



