194 PHYSIOLOGY OF NUTRITION 



300 g. of uninjured potato tubers produced from 1.2 to 2 mg. of carbon dioxide 

 per hour. After this rate had been determined each tuber was quartered, and 

 the pieces were left at the same temperature and in the same surroundings as 

 before. For the second hour after cutting, the rate of evolution of carbon dioxide 

 was 9 mg.; for the fifth, 14.4 mg.; for the tenth, 16.8 mg.; and for the twenty- 

 eighth, 18.5 mg. Then the. rate began to decrease. For the fifty-first hour 

 after cutting it was 13.6 mg., after four days it was 3.2 mg., and after six days it 

 had fallen to 1.6 mg., the original average rate obtained before wounding. 



Phosphates,'' which markedly accelerate alcoholic fermentation, have the 

 same effect upon respiration, which, as has been seen, is related to alcoholic 

 fermentation. 1 They thus accelerate both the anaerobic and the oxidation 

 phase of the respiratory process.^ 



The rate of plant respiration depends, furthermore, upon various internal 

 conditions, within the organism. In the first place may be mentioned the 

 relation between respiration and growth. The more rapidly a plant grows the 

 more oxygen does it absorb and the more carbon dioxide does it give ofi. As 

 will appear in the sequel (page2i8),airplantsexhibitthe so-called grand period of 

 growth, which may be represented by the grand curve of growth. A germinating 

 seedling grows slowly at first, but with increasing rapidity as it becomes older, until 

 a maximum growth rate is attained, after which growth proceeds more and 

 more slowly. The intensity of respiration is found also to be very low during 

 the early stages of growth; with increasing growth rates the respiratory process 

 is accelerated and this also reaches a maximum intensity and then declines. 

 Thus may be constructed a grand curve of respiration, the form of which is 

 practically identical with that of the grand curve of growth. This grand curve 

 of respiration was first shown by A. Mayer, who measured the oxygen absorbed. 

 Like results were obtained by Borodin and Rischavi,^ who determined the 

 amount of carbon dioxide -eliminated. 



The value of the respiratory ratio l-?^j does not remain constant during 



seed germination. Bonnier and Mangin^ showed that this value is unity for the 

 first phase of germination, but that it becomes smaller with increasing growth 

 rates. Palladin^ came to a similar conclusion from a study of the value of the 

 respiratory ratio for actively growing internodes cut from the stems of various 

 kinds of plants. In all these experiments the value of the ratio was less than 

 unity, which shows that growing organs absorb more oxygen than they give off 



•Iwanoff, Leonid, Ueber die Wirkung der Phosphate au£ die Ausscheidung der Kohlens&ure durch 

 Pflanzen. Biochem. Zeitsoh. 2S: 171-186. 1910. Iwanoff, Nicolaus, Die Wirkung der nutzlichen und 

 schadlichen Stimulatoren auf die Atmung der leben^en und abgeteteten Pflanzen. Ibid. 32: 74-96. 

 1911. 



> Zaleski, W., and Reinhard, A., Zur Frage der Wirkung'der Salze auf die Atmung der Pflanzen und auf 

 die Atmungsenzyme. Biochem. Zeitsoh. 27 : 450-473. 1910. 



> Mayer, A., Ueber den Verlauf der Athmung beimkeimenden Weizen. Landw. Versuchsstat., 18: 24S- 

 279. i87S. Borodin, 1875. [See note 3, p. 191.I Rischavi, L., Einige Versuche ttber die Athmung der 

 Pflanzen. Landw. Versuchsstat. 19: 321-340. 1876. 



* Bonnier and Mangin, 1884. [See note i, p. 192.] 



■ Palladin, W., Athmung und Wachsthum. (Auszug aus einer russisch'erscheinenden Arbeit.) Bef. 

 Deutsch. Bot. Ges. 4: 322-328. 1886. 



A 



This paragraph is omitted in the 7th Russian edition. — Ed. 



