1 5 2 RESPIRATION 



Drain * finds no clear correlation between catalase activity 

 and respiration of apples, and the same lack was observed 

 by Davis f in potato tubers suffering from the blackheart 

 disease. Rhine % observed that catalase markedly decreases 

 when oxygen is withheld from seeds by prolonged soaking 

 in oxygen-free water, and Morinaga § concluded that in- 

 crease in catalase activity is a function of free oxygen from 

 the facts relating to the germination of rice. Rice is grown 

 on swampy ground and is capable of germination and sub- 

 terranean growth in lower oxygen pressures than land plants. 

 Rice grains contain about one-tenth the amount of catalase as 

 wheat, oat, rye and like cereals which are grown on dry land ; 

 but when rice is germinated in aerobic conditions, the amount 

 of catalase rises to about seven-tenths of that of the other 

 cereals mentioned. If germinated in an atmosphere with a 

 low oxygen pressure there is still an increase in catalase, which 

 does not obtain if germinated in anaerobic conditions ; indeed, 

 the increment due to aerobic cultivation rapidly decreases in 

 the absence of oxygen. It was further observed that seedlings 

 with a higher catalase content use more oxygen in their growth 

 than those with a lesser amount of catalase. 



It is hardly possible to draw definite general conclusions 

 from these facts, many of which are contradictory. The 

 evidence does not show that catalase is chiefly concerned 

 in respiration, and the same applies to the oxidases, but 

 catalase may, as Lautz suggests, be a regulatory force pre- 

 venting excessive oxidation by removal of superabundant 

 hydrogen peroxide. 



FERMENTATION : ZYMASE AND CARBOXYLASE. 



An account of zymase and alcoholic fermentation has been 

 given in Vol. I. ; it is, however, desirable again to consider 

 the subject in view of the place it occupies in current opinions 

 on the mechanism of respiration. 



Zymase hardly requires introduction, it is the enzyme 



* Drain : '* Bot. Gaz.," 1926, 82, 183. 



f Davis : id., 1926, 82, 323. 



'I loc. cit. 



§ Morinaga : " Bot. Gaz.," 1925, 78, 73. 



