NITROGEN METABOLISM IN NORMAL AND IN 

 BLIGHTED SPINACH 



By Samuel L. Jodidi, Organic Chemist, Edward H. Kellogg, Scientific Assistant, 

 and Rodney H. True, Physiologist in Charge, Plant Physiological and Fermentation 

 Investigations, Bureau of Plant Industry. 



INTRODUCTION 



In view of the e\'ident derangement of the functions of nutrition in 

 spinach -bhght, it seemed necessary to undertake an investigation of the 

 more fundamental processes of synthetic metabolism in the hope of 

 learning in what way the disease causes injury. The purpose of this 

 paper is to present the results gained from a study of the nitrogen metabo- 

 lism. 



Owing to their great importance in plant metabolism, certain groups 

 of nitrogen-containing compounds demanded attention. The total 

 nitrogen, the polypeptids and the proteins, closely connected as they seem 

 to be with the fundamental activities of life in both plants and animals, 

 the nature and quantity of the nonproteins present, especially of the 

 amino acids, were studied in both healthy and diseased material. 



For a number of years it has not been unusual in plant and soil inves- 

 tigations to estimate the protein content of biological materials by deter- 

 mining their nitrogen content (usually by the Kjeldahl method) and 

 multiplying the nitrogen found by the factor 6.25. The literature con- 

 tains a great number of such protein estimations. Evidently the inves- 

 tigators maintained that the nitrogen present in plant and soil mate- 

 rials is made up solely or chiefly of proteins or protein-like bodies, whose 

 nitrogen percentage does not materially differ from that of proteins. 

 Schulze and his coworkers (41-45) were among the first to demonstrate 

 that such is not the case. They have shown, for instance, that a con- 

 siderable portion of the nitrogen contained in Irish potatoes (Solarium 

 tuberosum) and sugar beets, sometimes more than one-half, is made up 

 of nonproteins (acid amids, amino acids, etc.). So far as the writers are 

 aware, no similar systematic investigation concerning the character of 

 the nitrogenous compounds in spinach has been made. Hence, it seemed 

 of considerable importance to find out the nitrogen distribution in the 

 spinach under normal physiological conditions. Futhermore, it was of 

 interest to learn what changes, if any, had taken place in the nitrogen com- 

 pounds of the spinach under pathological conditions. 



Of special interest is the nature of the nonproteins (acid amids, amino 

 acids, polypeptids) occurring in spinach. These compounds may be 

 considered either as products of regressive metabolism in plants, or as 

 products of synthesis in the latter built up out of inorganic nitrogen 

 plant food, and are significant because of their food value, and the f unc- 



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