Nov. i8, 1918 Physiological Studies of Normal and Blighted Spinach 391 



seen that in the diseased plant the nitrogen of the leaves is higher than 

 that of either the roots or of the entire plant. A comparison of both 

 sections further shows that the percentage of nitrogen in the healthy 

 spinach (entire plant as well as leaves) is higher than in the corresponding 

 diseased tissues, but that the nitrogen of the diseased roots by way of 

 exception is somewhat higher than that of the healthy roots. If, as 

 Boncquet (6) has claimed, denitrification sometimes takes place in diseased 

 plant tissues whereby the nitrates are converted into nitrites and 

 ammonia, the possibility of the ammonia escaping as such is not alto- 

 gether out of the question. Such a proceeding would account for the 

 smaller percentage of nitrogen in the diseased spinach. 



PROTEIN NITROGEN OF THE SPINACH 



The significance of protein as an integral constituent of protoplasm 

 made it desirable to run a number of protein estimations of various 

 healthy and diseased spinach tissues. The method applied here was 

 originally proposed by Ritthausen (jp) and perfected by Stutzer (47). 

 One gm. of the finely powdered air-dry material was treated in a beaker 

 with 100 cc. of water, heated to boiling, and kept on the steam bath for 

 about 10 minutes. About 2 cc. of a concentrated potassium-alum solu- 

 tion were added, followed by 15 cc. of Stutzer's solution (corresponding 

 to 0.45 gm. of copper hydroxid), and the whole was well stirred. On 

 cooling, the insoluble residue was filtered off, washed with water, and 

 the nitrogen estimated according to Kjeldahl's method. In a few 

 instances, which will be mentioned, the following modification by Stutzer 

 was used: To i gm. of the substance were added 100 cc. of absolute 

 alcohol and i cc. of acetic acid, heated to the boiling point on a steam 

 bath, and allowed to settle, when the supernatant liquid was carefully 

 decanted through a filter. The substance which remained in the beaker 

 was now treated with 100 cc. of water, heated to boiling, etc., as already 

 outlined. The data obtained are summarized in Table IV. 



While the modified method of Stutzer yields a somewhat higher per- 

 centage of protein nitrogen than the ordinary Stutzer method, it will be 

 noticed by reference to the first section of Table IV that the proportion 

 of protein nitrogen in leaves 8 to 10 is practically the same as in the roots 

 II to 13. In other words, the protein nitrogen is practically uniform 

 throughout the healthy spinach plant (see No. 1-7). As regards the 

 actual quantities of protein nitrogen in the plants, as seen in the relation 

 of protein nitrogen to dry weight, the leaves are considerably richer than 

 the roots in both winter and spring samples. However, it will be noted 

 that the spinach collected in May, 191 6, shows a very much higher pro- 

 portion of protein nitrogen than that collected in December, 1915, and 

 January, 1916. The percentage of protein nitrogen calculated on dry 

 weight is, however, greater in the plants of the earlier collection. The 

 high relative percentage of protein nitrogen may perhaps be due to the 

 fact that the winter samples were not as mature as those collected in May. 



