122 PLANT RESPIRATION 



Many saprophytic fungi and bacteria thrive on solutions of 

 various organic substances and use up these substances in the 

 respiratory process. The question here arises whether all 

 these substances are worked up by way of the intermediate 

 stage of sugar, or whether, on the given nutrient solutions, 

 certain "trimmings" (Garnituren) of enzymes are formed in 

 microorganisms and consequently each nutrient substance is 

 resolved and oxidised by the temporary enzyme in a specific 

 way. The latest investigations of Kostychev and Afanassjewa^ 

 furnished a solution of this question. If, in the case of the 

 mold Aspergillus niger, the oxidation processes are checked by 

 lack of oxygen or even by the exclusion of oxygen, sugar appears 

 in the nutrient solution in the case of feeding with mannite. 

 glycerine, quinic acid, tartaric acid and lactic acid. Part of 

 the sugar formed from these substances is fermented to ethyl 

 alcohol and carbon dioxide when there is a deficiency of oxygen. 

 This is a new proof that the respiration of various nitrogen free 

 organic substances is effected not only by way of sugar as the 

 intermediate stage but also by the same coupled reactions 

 which take place in sugar nutrition.- These results agree with 

 the older statements of Czapek^ and other investigators as to 

 the relative value of various sources of carbon for the nutrition 

 of fungi. It is known that polyvalent alcohols, particularly 

 the hexavalent ones such as mannite and sorbite, represent 

 excellent sources of carbon; likewise the hydroxy acids. Sub- 

 stances with unoxidised carbon atoms are less suitable material 

 for respiration. For example, propionic acid is harder to use 

 than lactic acid but the latter is more difficult than tartaric acid. 

 Substances with a long, unbranched carbon chain are more 

 easily assimilated and used in respiration than substances with 

 a short or branched chain. Aromatic compounds are dis- 

 tinguished by an especially low nutritive value. On the con- 

 trary, hydro-aromatic alcohols such as inositol and quercitol 

 are very easily assimilated. All these regularities are easily 



' Kostytschew, S. Z. f. physiol. Chem. iii: 236. 1920; Kostytschew, S. und M. 

 Afanassjewa. Jahrb. £. wiss. Bot. 60: 628. 1921. 



2 The older theory of Diakonow is hereby completely refuted. There is not the slightest 

 difference to be noted between the products of anaerobic respiration with sugar on the one 

 hand and with nitrogen free non- sugars on the other. 



3 Czapek, F. Hofmeisters Beitr. i : 538. 1902; 2: 584. 1902:3:62. 1902. 



