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TEXTBOOK OF PLANT PHYSIOLOGY 



per cent. These figures show that even in case of starvation, a 

 part of the protein substances is preserved. The reserve proteins 

 of the seed were, of course, entirely disintegrated by this time. 

 The less labile protein substances of the protoplasm belong to the 

 group of nucleoproteids. They are complex proteins, representing 

 a combination of a simple protein with nuclein (see Art. 72). 



In germinating seeds the breaking down of proteins goes even 

 beyond the stage of amino acids. This complicates considerably 

 the general picture of the transformation of nitrogenous substances 

 at germination. Boussingault (1864) has pointed out the fact 

 that in germinating seeds, especially in legumes rich in reserve pro- 

 teins, there accumulates a large quantity of asparagine, an amide 

 of aspartic, or amido-succinic acid, 



CONH 2 • CH 2 • CHNH 2 • COOH. 



He has expressed the supposition that asparagine is analogous to 

 the amide which accumulates in the blood of animals, namely, urea, 

 NH2CONH2, and this forms a way of fixing ammonia, the 

 accumulation of which would expose the organism to the danger 

 of being poisoned with this toxic product. 



Boussingault's idea has been substantiated experimentally 

 through the work of Schulze (1875), who showed that, in reality, 

 asparagine is not the initial product of the decomposing protein 

 molecule, since there accumulates much more of it in seeds than 

 there was of aspartic acid in the reserve proteins, and that the 

 increase of asparagine, especially during the later stages of germina- 

 tion, is at the expense of the remaining amino acids. Thus, by 

 comparing the analysis of sprouts of peas 1-week old with those 3 

 weeks old, Schulze found the following quantitative changes of the 

 most important amino acids and asparagine: 



The amount of asparagine accumulating in the seedlings may 

 constitute up to 60 to 70 per cent of the total amount of protein 

 found in the seeds before germination. The highest percentage 



