THE CHEMICAL PROCESSES IN PLANT RESPIRATION 99 



Moreover, the identity of alcoholic fermentation of seed- 

 plants and molds with that of yeast has been successfully shown 

 through the isolation of acetaldehyde, which is undoubtedly 

 to be regarded as an intermediate product of yeast fermentation. 

 In the case of plants which possess stores of loosely bound oxy- 

 gen and a considerable quantity of oxidising enzymes, the 

 acetaldehyde is not completely reduced to ethyl alcohol even 

 when oxygen is excluded. Thus for example, Kostychev and 

 his coworkers^ were able to demonstrate the formation of 

 appreciable amounts of acetaldehyde by the anaerobic respira- 

 tion of poplar blossoms. Neuberg and his collaborators- have 

 caught acetaldehyde in the form of bisulphite compounds in 

 the case of the alcoholic fermentation of various fungi. 



It has already been pointed out that COo appears in the 

 anaerobic respiration of plants as the only gaseous product. 

 According to modern investigations the liberation of hydrogen, 

 as presupposed by earlier writers, especially when mannite is 

 used in respiration, is nothing but a result of bacterial infection.^ 

 On the other hand it is quite probable that products of anaero- 

 bic metaboHsm other than ethyl alcohol are formed in plants. 

 In the first place, it must be taken into consideration that the 



CO 



value of „ „ ^„ in the case of most aerobic plants does not 



correspond to the molecular proportion required by the equation 

 for alcoholic fermentation. Particularly, a considerable sur- 

 plus of CO2 is often formed. This condition can be explained 

 in two ways. 



I. Previous to the actual formation of alcohol a part of the 

 products of fermentation become altered in such a way that CO2 

 but no alcohol is formed from the decomposed sugar molecule. 



II. Alcoholic fermentation is not the only source of CO2 in 

 seed-plants which are respiring in the absence of oxygen. Other 

 processes take place by which CO2 is released but no alcohol 

 is formed. 



' Kostytschew, S., Hlibbenet, E. und A. Scheloumow. Z. f. physiol. Chem. 83: 105. 



1913. 



2 Cohen, C. Biochem. Z. 112: 139. 1920; Neuberg. C und C. Cohen. Ibid. 122: 204. 

 1921; also Eliasberg, P. Jour. d. Landw. Inst, in Petrogad 1921. P. 74- Russian. 

 (With Mucors.) 



3 Kostytschew, S. Ber. d. bot. Ges. 24: 436. 1906; 25: 178. 1907. 



