172 PHYSIOLOGY OF NUTRITION 



Ernst Schulze. 1 The following experiment with oat seedlings may serve as an 

 illustration of his work. The seedlings were first grown in light, then some of 

 them were used for analysis while the rest were placed in darkness. After a 

 week these also were analyzed. The numbers given below show the relative 



Original After a Week 



Plants in Darkness 



Total nitrogen 4.12 4 . 50 



Nitrogen of proteins 3.51 1.46 



Non-protein nitrogen 0.61 3.04 



amounts of protein and non-protein nitrogen found in each of the two lots of 

 seedlings. During the course of seven days in darkness more than half the 

 total amount of protein material is thus seen to have been broken down. 



The chemical nature of the protein decomposition products is dependent 

 upon various conditions; with different environmental conditions very different 

 decomposition products are produced. Oxygen is very important for the 

 progress of protein decomposition, but Palladin 2 has shown that this process 

 goes on also in the absence of oxygen. The following table shows the relative 

 rates at which protein decomposition occurred in wheat seedlings grown with 

 and without oxygen. The numbers denote percentages of total original protein 

 decomposed during the corresponding time periods. 



Percentage of Original Protein Decomposed 



Time Period Without Oxygen With Oxygen 



22 hours 1.1 .... 



1 day 3.9 7.9 



2 days 15.4 17.2 



3 days 26.1 



7 days .... 54 . 3 



The quantitative relations of the individual decomposition products are not 

 the same in the absence of oxygen as in its presence. In the latter case asparagin 

 is the main product while tyrosin and leucin are formed only in very small 

 quantities. In the absence of oxygen, however, tyrosin and leucin accumulate 

 to a marked degree while the amount of asparagin formed is quite negligible. 

 This fact shows that the primary products of protein hydrolysis are formed only 

 in the absence of oxygen. As long as asparagin was considered as one of these 

 primary products it was impossible to understand how protein hydrolysis 

 within the plant body results in the formation of asparagin, while the hydrolysis 

 of plant proteins with acids produces but a negligible amount of aspartic acid 

 (see page 161). The experiments described above explain this; it has been 

 shown that asparagin arises during synthetic processes. Borodin 3 had already 



1 Schulze, E., Steiger E., and Bossard, E. Untersuchungen über die stickstoffhaltigen Bestandtheile 

 einiger Rauhfutterstoffe. Landw. Versuchsst. 33: 80-123. 1887. [Schulze, E., Ueber die Methoden, 

 welche zur quantitative Bestimmung der stickstoffhaltigen Pflanzenbestandtheile verwendbar sind. Ibid. 

 33: 124-145- 1887.] 



2 Palladin, W., Ueber Eiweisszersetzung in den Pflanzen bei Abwesenheit von freiem Sauerstoff. Ber. 

 Deutsch. Bot. Ges. 6: 205-212. 1888. Idem, Ueber Zersetzungsproducte der Eiweissstoffe in den Pflan- 

 zen bei Abwesenheit von freiem Sauerstoff. Ibid. 6: 296-304. 1888. 



3 Borodin, I. P., On the conditions for the accumulation of leucin in plants. [Russian.] Trav. Soc. 

 Imp. Nat. St.-Petersbourg 16 (Protocole) : 60-73. 1885. 



