745 



■>• 



Constantine Sorokin 



lies, perhaps, with the fact that most of the above observations 

 were made on specially synchronized algal ce11s« 



There has been wide-spread concern (25-2o) ^^3^ ^^g observed ^ 

 variations in metabolic activity may be due to synchronization s 

 technique; that they are not characteristic of the normal life \ 

 cycle of cells but are caused by the synchronizing agent. The 

 effect of a synchronizing agent on the subsequent activity of 

 cells cannot be denied any more than can the effect of any other 

 environmental condition. However, a decline in metabolic activity 

 with the age of cells was observed also for the naturally syn- 

 chronized green colonial alga Hydrodictvon (29) and for individual 

 cells of Amoeba (30) and Tetrahymena (3«), 



Another technique used in studies of the relative photosyn- 

 thetic activity in young and old algal cells consists of 

 separation of cells of an originally nonsynchronized suspension 

 into fractions by centrifugation. After centrifugation, the 

 small cell fraction presumably consists mostly of young cells and 

 the large cell fraction of predominantly old cells. Before being 

 centrifuged from a nonsynchronized suspension, these two groups 

 of cells are subjected to the same environmental conditions and 

 the difference in their performance must, therefore, be attri- 

 buted only to the difference in the age composition of these 

 groups. 



Using this technique, the late Or, R. Emerson studied quantum 

 efficiency of small and large cells and made two comments. In 

 one report in 195^ (32)^ he stated that large cells have higher 

 quantum requirement per molecule of photosynthetic oxygen produc- 

 tion. In 1957 (33), he reversed his opinion, stating that 

 difference in quantum efficiency of large and small cells is 

 transient and therefore illusory. Neither report was published 

 in detail, and no description of the technique used by 

 Or. Emerson is available. Or. Emerson's observations, and parti- 

 cularly his denial of the age changes in photosynthetic activity, 

 probably contributed to the delay in the acceptance of the 

 concept of aging of cells as a universal biological reality. 



Centrifugation technique may lead to false interpretations 

 unless some basic conditions are observed. These conditions 

 include: 



1. A wide diversification in cell sizes of nonsynchronized 

 suspension to be subjected to centrifugation; 



