562 RESPIRATION AND FERMENTATION 



Both the older and later researches 1 have shown that the respiratory curve 

 possesses the character indicated, while the existence of an optimum is still un- 

 certain and the latter must in any case be near the critical temperature. In 

 Clausen's and Ziegenbein's experiments the plants were apparently temporarily 

 injured and did not immediately assume their original respiratory activity when 

 returned to the previous temperature, as should properly be the case. Hence the 

 curve constructed by these authors was a secondary one resulting from prolonged 

 exposure, and was not due to the direct and immediate action of the rising tempera- 

 ture. Respiration may be twenty to forty times more active at the maximum 

 temperature than it is at o c C., and the activity frequently increases in geometric 

 proportion as the temperature rises to the maximum, while the respiratory quotient 

 C(X : O 2 usually but not always remains constant. 



Owing to the influence of temperature upon growth and hence ulti- 

 mately upon the mass of respiring protoplasm, a certain permanent optimal 

 temperature exists for growing plants at which the total amount of 

 respiration is greatest, while above this point the higher respiratory 

 activity becomes ultimately unable to counterbalance the diminished bulk 

 due to the decreased growth. This optimum lies between 25 to 30 C. 

 in the case of alcohol-producing bacteria, and a similar optimum has been 

 observed in other bacterial fermentations in which the fermentative activity 

 increases as the bacteria increase in numbers. According to Chudiakow 2 

 the curves of oxygen- and intramolecular-respiration follow a parallel 

 course as the temperature alters, and similarly when the growth of 

 Saccharomyces is inhibited, the fermentative activity continually increases 

 up to the maximum temperature. It is not however permissible to make 

 any generalization from this fact, for fermentative activity may be a special 

 process which is only indirectly connected with anaerobic respiration 

 (Sect. 102), and in deciding this question it would be of the utmost 

 importance if at different temperatures it were found possible to distinguish 

 between these two functions. The production of oxalic acid by Aspergillns 

 is markedly diminished at high temperatures, owing to the increased 

 oxidatory activity, and other oxidizing fermentations may be modified 

 in a similar manner by changes of temperature. 



Light. All critical experiments have shown that as a general rule 

 respiration is not markedly influenced by changes in the illumination. 

 Bonnier and Manghr 5 state that light commonly induces a slight diminution 



1 Kreusler, Lanclvv. Jahrb., 1887, Bd. xvr, p. 746; iSSS, Bd. xvir, p. 172; 1890, Bd. XIX, 

 p. 663 ; Clausen, I.e., 1890, p. 894; Ziegenbein, I.e., 1893; Chudiakow, Landw. Jahrb., 1894, 

 Bd. xxili, p. 349; Bonnier ct Mangin, Ann. d. sci. nat., 1884, vi. sen, T. xvn, p. 271; 1884, 

 T. xvni, p. 359. 



2 Chudiakow (Landw. Jahrb., 1894, Bd. xxm, p. 350) has shown that Amm's contradictory 

 conclusions (Jahrb. f. wiss. Bot., 1893, Bd. xxv, p. 27) are not justifiable. 



3 Bonnier et Mangin, Ann. d. sci. nat, 1884, vi. sen, T. xvn, p. 281 ; T. xviu, p. 353; also 

 Elfving, Einwirkung d. Lichtes auf Pilze, 1890, p. 98; Puricwitsch, Bot. Centralbl., 1891, Bd. XLVII, 



