Nov. i8, 1918 Physiological Studies of Normal and Blighted Spinach 393 



Table IV, second part, shows that the protein nitrogen when referred 

 to the total nitrogen in the diseased spinach is not distributed uniformly, 

 the percentage in the roots being higher than that in the leaves. Here 

 the samples collected in December and January have a considerably 

 lower proportion of protein nitrogen referred to total nitrogen than the 

 sample gathered in May. When referred to the dry weight of the plant 

 material, the protein nitrogen of the roots exceeds that in the leaves in 

 both winter and spring collections, the quantity present in the spring 

 samples being clearly less than in those taken in winter. In this latter 

 respect the diseased plants differ from the normal ones. The greater 

 proportion of protein nitrogen to total nitrogen may indicate that the 

 spring sample was in a riper state than the former winter samp'le. 



When the first section of Table IV isco mpared with the second section, 

 it is seen that the diseased spinach is not only able to build up protein 

 but, with one exception, shows even a higher percentage of protein 

 nitrogen (calculated on total nitrogen) than the healthy spinach, this 

 being true of the leaves, the roots, and the entire plant. In case the 

 protein nitrogen is related to the dry weight of the plant tissues, the 

 situation is reversed as regards the entire plant and the leaves, the 

 roots only showing a higher content in the diseased plants. This is 

 true for both winter and spring material. So far as animal tissues are 

 concerned, it was shown by Cramer (11) that certain rapidly growing 

 cells and tissues build up protoplasm with less complex organic com- 

 pounds (like proteins, etc.) than more slowly growing tissues. 



From the data here presented it would seem that in spinach collected 

 both in winter and spring the actual number of grams of protein nitrogen 

 is greater in a given dry weight of healthy tops than in a like quantity of 

 diseased material, this relation being plainly reversed in the case of the 

 roots. It also seems clear that of the total nitrogen content a greater 

 percentage is in protein form in the diseased than in the normal plants, 

 the case of the leaves in the spring material being the only exception. 

 It is further indicated that all winter material, diseased and healthy, is 

 somewhat richer in protein nitrogen than the corresponding material 

 collected in the spring. 



NONPROTEIN NITROGEN OF THE SPINACH 



The nonprotein nitrogen is usually found by subtracting the protein 

 nitrogen from the total nitrogen. It seemed, however, desirable to make 

 direct estimations of the nonprotein nitrogen as a check on the protein 

 determinations. We proceeded as follows: The combined filtrate and 

 washings from the copper precipitate, as obtained in the protein estima- 

 tion according to Stutzer's method, were usually acidulated, concentrated 

 on the water bath, quantitatively transferred to a Kjeldahl flask, and the 

 nitrogen estimated as usual according to the Gunning modification of 

 Kjeldahl's method. The results obtained are reported in Table V. 



