89 



Palladin^^ and his collaborators have taken up the question of 

 the role of the chromogens and the oxidases in the respiration 

 of the plant. They have followed out the general line of thought 

 first conceived by Reinke. They have published many papers 

 on the subject which cannot be abstracted here in detail, but a 

 general outline of their results and conclusions will be given. 

 In the anaerobic respiration of seeds, alcohol, acetone, and sub- 

 stances of aldehyde nature were obtained. Oxygenase increases 

 with the growth of the part containing it. Both oxygenase and 

 peroxidase are much increased by feeding the plant freely with 

 sugars. The chromogens also increase under such circumstances. 

 Palladin made a systematic search for the respiratory chro- 

 mogens, and found they were very wide-spread and were gen- 

 erally red or brown when oxidized. To detect the chromogens 

 he ground the plant material under water and thus obtained a 

 light-colored solution to which he added peroxidase (from horse- 

 radish) and hydrogen peroxide; if the chromogen were present, 

 it was soon oxidized and caused the solution to darken. In this 

 manner he found that of seventy-one different plants examined, 

 sixty-seven contained chromogens and that the parts ,with an 

 active respiration like flowers, young shoots, etc., showed the 

 greatest amount of respiratory chromogen. Chloroformed plants 

 soon began to show coloration due to the oxidation of their 

 chromogens. These chromogens seem to be derivatives of the 

 cyclic series, and Palladin considered that they often occur in 

 the form of glucDsides, which, by the action of glucoside-splitting 

 enzymes, are separated from the sugars and then take up oxygen 

 by the aid of the oxidases, thus becoming colored. During the 

 normal life of the plant there is a coordinated action of these 

 hydrolytic, oxidizing, and reducing enzymes, which prevents 

 oxidation of the chromogens, but during narcosis or after death, 



*^ Palladin: (a) Die Atmungspigmente der Pflanzen. Zts. Physiol. Chem. 

 55: 207. 1908. (&) Die Verbreitung der Atmungschromogene bei den 

 Pflanzen. Ber. Bot. Gesell. 26a: 378. 1908. (c) Ueber das Wesen der Pflanzen- 

 atmung. Bioch. Ztsch. 18: 151. 1909. (d) Ueber die Bildung der Atmungs- 

 chromogene in den Pflanzen. Ber. Bot. Gesell. 26a: 389. 1908. (e) Die Arbeit 

 der Atmungsenzyme der Pflanzen, etc. Zts. Physiol Chem. 47: 407. 1906. (/) 

 Ueber die Prochromogene der Pflanzen-Atmungschromogene. Ber. Bot. Gesell. 

 27: loi. 1909. 



