THE BIO-CHEMISTRY OF ANIMALS AND PLANTS 685 



use amino acids themselves or higher cleavage products for their 

 protein synthesis. There has been very little work done on the 

 metabolism of carnivorous plants, and this point has not been 

 investigated. That plant organisms exist which produce their 

 protein from the higher cleavage products alone has, however, 

 been made clear b}' the researches of Beijerinck, who proved 

 that the alga living symbiotically with Physcia parietina requires 

 peptones {i.e. albumoses) for its normal growth. 



Higher Plants. — Relatively little is yet known about the 

 protein synthesis in plants containing chlorophyll. The study 

 of the processes occurring during germination has attracted 

 many investigators, and has furnished most useful results. The 

 ripe seeds nearly always contain a large store of protein. As 

 soon as germination begins great changes take place in cells. 

 The proteins are decomposed b}^ the action of proteol3^tic 

 ferments, the existence of which, during germination, has been 

 definitely proved. B}^ the action of these ferments the higher 

 cleavage products first obtained from the proteins are finally 

 converted into simple amino acids, which are partly at least 

 made use of at once b}^ the growing plant. We may compare 

 the process of germination with that occurring during digestion 

 in the animal body. In both cases the complex food protein is 

 first decomposed into simpler cleavage products, and it is from 

 these that the organism reconstructs the protein matter of its 

 protoplasm. A long series of amino acids, leucine, tyrosine, 

 aspartic acid, glutaminic acid, arginine, lysine, histidine, etc., 

 have been isolated from germinating seeds. A peculiar occur- 

 rence is the formation of asparagine and sometimes of glutamine, 

 substances which have not been observed in any artificial 

 protein hydrolysis. By allowing seeds to germinate in the 

 dark, i.e. under normal conditions, large amounts of these two 

 substances ma}^ be produced. The significance of asparagine 

 formation is not yet fully understood. Pfeffer has shown that 

 the increase of the asparagine is coincident with the decrease of 

 carboh3^drate formation in the absence of light, which stands in 

 close relationship to the protein synthesis, the absence of which 

 entails an accumulation of amino acids. It is possible that 

 asparagine represents a transition stage in the formation of 

 other nitrogenous substances, or perhaps that it is connected 

 with carbohydrate and fat formation. This view is confirmed 

 by certain observations made upon tyrosine. This amino acid 



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