835 



THE ROLE OF NITROGEN AND ITS COMPOUNDS IN 

 PLANT-METABOLISM. 



Part ii. — The Non-Protein Nitrogen in Seeds. 



By James M. Petrie, D.Sc , F.I.C., Linnean Macleay Fellow 

 op the Society in Bio-Chemistry. 



(From the Physiological Laboratory of the University oj Sydney. ) 



i. Previous work on the subject. 

 ii. Discussion of Methods used for precipitation of Proteins — 



copper hydroxide, tannin, alcohol, 

 iii. The Non-Protein Nitrogen in a series of thirty different seeds, by 

 alcohol precipitation. 



i. Until a few years ago the nitrogen of seeds was by many 

 authorities looked upon as existing entirely in proteins. The 

 total nitrogen found by analysis was multiplied by a factor, 6 3 

 (obtained from the average per cent, of nitrogen in protein) and 

 the product written as proteins. We find this still not uncom- 

 mon at the present time. The purpose of this paper, therefore, 

 is to emphasise the fact that such is not the case; and also to 

 record some remarkable results, in which it may be seen that, in 

 some seeds, proteins account for little more than one-half of the 

 nitrogen. 



As is well known, when seeds commence to germinate, the 

 insoluble protein-substances are changed by proteolytic ferments 

 which suddenly appear by the activation of the pre-existing 

 zymogens. We thus have all the soluble protein hydroxy tic 

 products, viz., proteoses, peptones, and amino-acids, etc., present 



