SYNTHESIS IN THE PLANT 333 



alcohol, in which prolamins are insoluble, and ether. The 

 ether is added in order to make the precipitation more com- 

 plete and also to hold any fats which may have been ex- 

 tracted by the alcohol. 



THE SYNTHESIS OF PROTEINS IN THE PLANT. 



In view of our limitations as regards the chemistry of pro- 

 teins, it is not surprising that we are in almost complete ignor- 

 ance respecting the synthesis of these substances in plants. 



It is generally agreed that the leaves are the important 

 centres of protein formation, and they show a periodicity in 

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

 du Sablon 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 requisite nitrogen is obtained, not from the air the 

 Leguminosae are here excluded but from the salts contained 

 in the water absorbed by the roots ; thus the fertility of soil, 

 especially with regard to nitrates, is most important, as has 

 been shown by direct experiments. J 



In passing, it may be remarked that some plants, at any 

 rate, can make use of salts of ammonium as a source of 

 nitrogen. Hutchinson and Miller found this to be true under 

 conditions of culture which precluded the presence of nitrates 

 in the soil. In this respect, however, all plants do not behave 

 alike ; whilst some will grow equally well whether supplied 

 with nitrates or ammonium salts, others flourish best when 

 supplied with the former, and others seemingly prefer am- 

 monium salts to begin with and then nitrates. 



Since protein formation takes place particularly in the 

 leaves, it might be supposed that light is an important and di- 

 rect factor in its synthesis. Indeed earlier workers, Schim- 

 per || for example, considered this to be so, but more recent 

 investigations tend to show that the synthesis of proteins 



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



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



JWhitson and Stoddart: "Ann. Rep. Wisconsin Exp. Sta.," 1904, 193. 



Hutchinson and Miller: "Journ. Agric. Sci.," 1909, 3, 179. 



|| Schimper : " Flora," 1890, 73, 207. 



