OXIDASE AND CATALASE 99 



If respiratory processes are esentially enzymatic, it is 

 natural to suppose that the respiration intensity would increase 

 in the presence of accelerators : various substances have been 

 so described, amongst them being phosphates * which are im- 

 portant accelerators in zymase action, f 



Palladin looks upon lipoids as being of the nature of co- 

 enzymes, since the more they are extracted from the plant 

 tissue, the greater is the reduction in the intensity of respiration 

 although not in an exact proportion. J 



Galitsky and WassiljefT observed that the addition of 

 boiled water extracts of bean seeds and wheat grains increased 

 the output of carbon dioxide in living and in dead seedlings to 

 a degree depending on the acidity of the culture medium : in 

 neutral cultures the increase reached 117 per cent, whilst in a 

 slightly alkaline medium an increase of 86 per cent obtained 

 as compared with an increase of 60 per cent in a slightly acid 

 medium. 



Of the enzymes mentioned, oxidase and catalase are the 

 more prominent, numerous observations having been made on 

 their distribution and relation to the oxidative aspects of 

 respiration. Appleman || found that the oxidase content of 

 the expressed juice of the potato is not indicative of the in- 

 tensity of the respiration of the tuber, whilst the catalase 

 activity shows a striking correlation. Similarly for sweet corn, 

 in which instance the respiration in the milk stage is high 

 when first collected but in storage rapidly decreases, the de- 

 crease being accompanied by a nearly proportional fall in cata- 

 lase activity. In the pine-apple, Reed 11 found that oxidase and 

 catalase are independent ; the amount of the former remains 

 constant during ripening of the fruit whilst the catalase in- 

 creases. In the wheat and certain allied plants, the embryo 

 shows a twenty-eight to twenty-nine-fold greater catalase and 

 oxidase activity than the endosperm, and this also holds for 

 the intensity of respiration. In air-dry fruits of Andropogon 



*Iwanoff: " Biochem. Zeitsch.," 1910,25, 171; 1911,32,74; Zaleski and 

 Reinhard : id., 1910, 27, 450. 

 t See Vol. I., p. 379. 



J Palladin : *' Ber. deut. hot. Gesells.," 1910, 28, 120. 

 Galitzky and Wassiljeff : Id., 182. 



|| Appleman: " Amer. Journ. Bot.," 1916, 3, 223 ; 1918, 5, 207. 

 IT Reed : " Bot. Gaz.," 1916, 62, 409. 



7* 



