676 



temporarily arrested. Pozzi-Escot' furnishes an example of this when dis- 

 cussing the Philothion. "Reductases," he thinks, which are identical with 

 Loew's catalase, "are distributed everywhere like oxydases, and act antag- 

 onistically" . . . De Rey-Pailhade has proved that reductases are 

 quickly destroyed by an oxydase in the presence of free oxygen, and, con- 

 versely, Pozzi-Escot proves that, under certain circumstances, the action of 

 an oxydase can be "paralyzed," when the reductase is present in great ex- 

 cess. Thus, in temporary fluctuations in the cell contents, a reductase can, 

 for the moment, make the oxydase ineffective, and conversely. Pozzi- 

 Escot perceives the most important role of the reductases to be their action 

 on H, Oo in the processes of respiration as well as in photo-synthesis. 



Antiferments occur in other cases, as Czapek-, for example, has dem- 

 onstrated. He found an arrestment in the further oxidation of the homo- 

 gentisin acid, originating from tyrosin, in organs stimulated geotropically 

 or heliotropically by the presence of an anti ferment. 



In general, we perceive from the results of cultivation and some experi- 

 mental investigations, that light and heat favor catabolism, i. e., disposition 

 of groups of solid reserve material, while darkness and cold either maintain, 

 or cause an increase in the amount of colloidal food materials. 



Under normal climatic conditions, the time at which prevailing condi- 

 tions in the cell contents exhibit the conditions characteristic of the 

 destructive activity, lies actually in the colder seasons of the year. We 

 find processes of germination especially in autumn and spring, but, on the 

 other hand, constructive activity, i. e., the deposition of reser\^e materials, 

 in the summer. 



The necessary regular succession of these periods depends, however, 

 not only on the weather but also on all the nutritive factors, as, for example, 

 the supply of water, the amount and constitution of the nutrients, and, 

 besides this, on differences in cultivation, viz., pruning, etc. A number of 

 diseases offer examples for the last point, i. e., when the organism is com- 

 pelled, by the sudden removal of considerable amounts of the plant body 

 Cbranches and leaves), to mobilize again the stored material at a time when 

 the period of storing should prevail and, thereby, to return to the vegetative 

 period for the formation of new shoots. In regard to the supply of food 

 we find, for example, that excessive amounts of nitrogen postpone the 

 period of storing up reserve materials since growth is continued beyond 

 the normal size. 



Thus," the enzymatic work is postponed ; the mobilizing enzymes now 

 prevail and the plant, with organs in active growth, enters upon a period 

 of weather which, in the normal course of events, demands mature plant 

 parts, rich in reser\^e materials. It becomes, therefore, susceptible to para- 

 sitic and non-parasitic attacks. 



1 Pozzi-Escot, E., The Reducing- Enzymes. American Chem. Journ., Vol. XXIX, 

 1903, p. 517; cit. Bot. Centralbl. 1904, No. 49. 



2 Czapek, F., Antifermente im Pflanzenorganismus. Ber. d. Deutsch. Bot. Ges. 

 1903. Vol. XXI, p. 229. 



