OXYGEN RESPIRATION 



pierced by the radicle.^ Analogous phenomena are to be found 



in the respiration of yeast- and some of the Mucoraceae^ 



Here there is oxygen respiration as well as alcoholic fermenta- 



, CO2 . 

 tion and -7c— is greater than i. 

 U2 



COo 

 III. Various fluctuations in the value ot ^ can ongmate 



as a result of the given respiratory material having a percentage 

 composition different from that of sugar. This is the most 



COo 



common basis of "abnormal" size of -^^—J For example, 



after the complete consumption of the sugars and by way of a 

 satisfactory substitution, the plants begin to burn the protein 

 material of their protoplasmic framework, and in consequence 



CO 



-^ falls to 0.70-0.80: that is to say, protein is poorer in 

 O2 



oxygen than sugar and so uses up, for complete combustion 

 to CO2, H2O and N, a greater quantity of atmospheric oxygen 

 per unit weight. In other cases there is consumed the ethyl 

 alcohol which is split off under unfavorable conditions of 

 aeration (see above) . The total combustion of alcohol involves 



a lower value of -^ : 

 U2 



CH3-CH0OH + 3O2 = 2CO0 + 3H2O. 



--— = = 0.66. 

 O2 3 



This process stands out as the normal phenomenon in the 

 germination of pea seeds up to the time that the compact seed 

 coats burst. The alcohol which is split off in the first stages of 

 germination (see above) is burned with a considerable oxygen 



iPotowzow, V. Untersuch. uber Pflanzenatmung. 1901 [Russian]; Kostytschew, S. 



Biochem. Z. 15: 164. 1908; Physiol.-Chem. Untersuch. uber Pflanzenatmung. 1910. 



[Russian.] 



= Buchrer, E., H. Buchner und M. Hahn. Die Zymasegarung. P. 3S0. 1903; Kosty- 

 tschew, S. und P. Eliasberg. Z. f. physiol. Chem. in : 141- 1920. [Meyerhof, O. Bio- 

 chem. Z. 168 : 43- 1925.1 



3 Kostytschew, S. Zentralbl. f. Bakt., Parasitenk. u. Infektionskrankh (U). 13: 490. 



1904. . , . 



f Another cause for marked fluctuations is the amount of water contamed in 

 the tissues, according to Mayer, A. et L. Plantefol. Compt. rend. 181: 131- 

 132. 1925. In general the respiratory quotient varies inversely with the total 

 amount of water imbibed. — Ed. 



