CHAPTER IV. 

 THE SYNTHESIS OF PROTEINS. 



IN view of our limited knowledge of the chemistry of proteins, 

 the degree of our ignorance respecting their synthesis in plants 

 is not surprising. 



It is generally agreed that the leaves are the important 

 centres of protein formation, and they show a periodicity in 

 their nitrogen content. Otto and Kooper* and Le Clerc du 

 Sablonf found that there is a gradually decreasing amount of 

 nitrogen from the spring to the autumn, and that leaves of 

 several different plants, even in different stages of development, 

 exhibit a greater nitrogen content in the morning than in the 

 evening. 



The supply of nitrogen is an essential factor, and this 

 element must be presented in a form suitable for the nutritive 

 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 under certain 

 conditions, but the best results obtain from the employment 

 of peptone, a culture solution of peptone and sucrose giving 

 177*4 P er cent increase in dry weight after the completion of 

 fermentation. | 



There is, however, much variation shown by the lower non- 

 green plants in this respect, hardly a matter for surprise in such 

 metabolic gymnasts ; Bacillus coli will flourish on a diet contain- 

 ing 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 considers that in general ammonium salts, and 

 especially the ammonium salts of organic acids such as quinic 



* Otto and Kooper : " Landwirthsch. Jahrb.," 1910, 39. 

 f-Le Clerc du Sablon : " Rev. Gen. Bot.," 1904, 16, 341. 

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

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



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