74 



PLANT PHYSIOLOGY 



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. The increase 

 of asparagine, especially during the later stages of germination, 

 is at the expense of certain of the remaining amino acids. 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 

 of aspartic and the related glutamic acids does not exceed 20 to 

 25 per cent. 



Asparagine, accordingly, is not the initial product of hydroly- 

 sis, but the result of union of nitrogenous substances with a carbon 

 chain. This view received a final substantiation through the 

 experiments of Prianishnikov. On germinating seeds in solu- 

 tions of ammonium salts, he observed the synthesis of asparagine 

 in seeds not only from the amino acids present during 

 germination but also from ammonia supplied from without. In 

 this connection, it is interesting to note that not all seeds bring 

 about this synthesis with equal ease. It proceeds readily in 

 seeds rich in nonnitrogenous reserves, such as the carbohydrates 

 and fats, e.g., in the seeds of graminaceous plants. In seeds of 

 leguminous plants, in which there are large amounts of reserve 

 proteins but in which the carbohydrate content is comparatively 

 small, asparagine can be synthesized from ammonium salts 

 only when calcium carbonate is supplied at the same time, which 

 neutralizes the free acid. But the seeds of lupine, which are very 



