84 THE SYNTHESIS OF PROTEINS 



insolation. Bovie * draws attention to the efficiency of the 

 extreme ultra-violet rays, the so-called Schumann rays, and 

 points out that the photolysis of protein and of protoplasm 

 increases with the diminution in the wave-length of the in- 

 cident light ; in the extreme ultra-violet region, the amount 

 of chemical change is proportional to the product of the light 

 intensity and the time of exposure. 



It will be remarked that these observations refer not directly 

 to protein synthesis but rather to the action of 'these qualities 

 of radiant energy on the general growth of the plant, a subject 

 which will be considered later. 



The supply of nitrogen is an essential factor, and this 

 element must be presented in a form suitable for the nu- 

 tritive processes of the plant. Thus amongst the non-green 

 plants, Saccharomyces is unable to make use of nitrates and 

 but little use of simple amines ; urea can be assimilated in 

 certain conditions, but the best results follow the employ- 

 ment of peptone, a culture solution of peptone and sucrose 

 giving 177-4 per cent, increase in dry weight after the com- 

 pletion of fermentation. f 



There is, however, much variation shown by the lower 

 non-green plants in this respect ; Bacillus coli will flourish on a 

 diet containing salts either of ammonia, of simple amides or 

 of amino acids, whilst the cholera bacillus can apparently make 

 no use of ammonium salts but is able to utilize amino acids. 

 For the Fungi, Boas J considers that in general ammonium 

 salts, and especially the ammonium salts of organic acids such 

 as quinic acid, are better than amino acids as a source of nitro- 

 gen in protein synthesis. He points out that such feeding 

 experiments should be brief, in order to avoid secondary, 

 especially proteolytic, changes, and that the reaction of the 

 culture medium is all-important. Acidity may inhibit the 

 growth of many fungi, so that if ammonium salts of inorganic 

 acids be used as a source of nitrogen, the observed results 

 may be due not to the inability of the plant to employ the 



* Bovie : " Bot. Gaz.," 1916, 61, 1. 



t Bokorny : " Chem. Zeit.," 1916, 40, 366. 



\ Boas : " Biochem. Zeit.," 1918, 86, no, 



