5t.6 



B. A. RUBIN 



placement is part of the process of ripening of the fruit (Fig. i). Not uncommonly, 

 substantial changes in enzymic systems may be observed after short intervals of 

 time. According to Todd, in the period of active grouth of the tubers of the 

 potato, cytochrome oxidase occupies the central place in its respiration, while 

 after harvesting the tubers this is occupied by tyrosinase. However, according 

 to the findings of our laboratory, jusl before the potato tubers emerge from the 

 resting stage there is a considerable activation of their flavoprotcin oxidase and 

 also of cytochrome oxidase with a weakening of the activity of the proteins. 



Sisakyan [13] showed that cytochrome oxidase retains its activity in wheat 

 shoots only until they have completed the stage of vernalization after which the 

 enzyme cannot be found. The leaves of the plants, however, again show cyto- 

 chrome oxidase activity when they are two months old. James [14] has estab- 

 lished that the growing zone of the rootlets of barley during the first 4-5 days of 



Fig. 2. The distribution of polyphenol oxidase in the cells of apples at different 



stages in their development. I — In the plastids, II — In the juice. III — In the juice, 



as "(', of total activity. 



life, respires owing to the action of cytochrome oxidase which is then replaced 

 by ascorbinase. According to Beevers & Gibbs [15] the route of direct oxidation 

 of glucose, which is hardly ever used in the tissues of young fruit plants, 

 accounts for about half the total respiration of the same object in a more mattire 

 state. 



One may also observe substantial changes, associated with growth, in the 

 enzymic systems which catalyse glycolytic processes in the tissues of higher 

 plants. Thus, according to Ducet & Rosenberg [16], in the leaves of yoimg plants 

 under anaerobic conditions CO prevented the evolution of CO2, while in fruit- 

 bearing plants this factor had the opposite effect. Intracellular locaUzation of 

 enzymes may serve as a factor which further strengthens the heterogeneity of the 

 biocatalytic systems of plants. In recent years this problem has attracted great 

 attention [17, 18]. 



In the work of E. V. Artsikhovskaya in the A. N. Bakh Institute of Bio- 



