THE CHEMICAL PROCESSES IN PLANT RESPIRATION 14I 



his coworkers^ who have effected a regular transformation of 

 the ammonium salts of «-keto- or a-hydroxy-acids into amino 

 acids of the corresponding constitution by experiments in which 

 blood is passed through isolated liver. This work indicates the 

 course of the biological synthesis of amino acids. 



On the basis of these investigations it is most probable that 

 the greater part of the malic acid of seed-plants is formed in 

 the process of formation or deaminization of asparagine. 

 Frequently, perhaps because of a deficiency of nitrogen, all the 

 malic acid cannot be worked into asparagine. The excess of 

 malic acid is then destroyed by oxidation processes leading to 

 the formation of COo, but this is not a direct or normal respira- 

 tory process. The oxidation of plant acids is much more like 

 the "protein respiration" already mentioned [see page 123]. 

 The following curious phenomenon, observed by Warburg and 

 Negelein,^ may be noted in this connection. It was found that 

 an excess of CO2 is given off during the assimilation of nitrates 

 by the single-celled alga Chlorella vulgaris. The formation of 

 CO2 is not a real respiratory process. It can be sharply sepa- 

 rated from the respiratory release of CO2 by means of certain 

 toxic effects. The assumption is not precluded that in this 

 case there is an oxidation of plant acids in connection with the 

 formation of protein. 



The studies of Ruhland and Wetzel,^ Ullrich'* and A. Smir- 

 noff^ are decidedly in favor of a connection of the formation of 

 organic acids with the transformation of plant proteins. 



In the case of the lower plants, at the most only traces of 

 malic acid can be formed. It is also to be noted that aspara- 

 gine is never formed in the fungi and bacteria. 



As for citric acid with its branched carbon chain, a direct 

 transformation of sugar into this acid during the respiratory 

 process is not very probable. It is worthy of note that in the 

 formation of amino acids, branched chains are synthesized from 



1 Embden, G. und E. Schmitz. Biochem. Z. 29: 423. 1910; 38: 393. 1912; Kondo, K. 

 /feid. 38:407. 1912; Fellner. Ibid. 38:414. 1912. 



2 Warburg, O. und Negelein. Biochem. Z. no: 66. 1920. 



3 Ruhland, W. und K. Wetzel. Planta. i : 558. 1926. 

 < Ullrich, H. Ibid, i : 565. 1926. 



5 Smirnoff, A. Zur Frage des Stoffwechsels im Tabakeblatt im Laufe seiner Entwickel- 

 ung. 1026. Russian. 



