FOOD 125 



the rate of evolution of carbon dioxide from seedlings and buds 

 to be about doubled with an increase of io° C, and Kuijper 

 found the law to apply at temperatures between 0° C. and 20° C. 

 in the pea and wheat, and between 0° C. and 25 C. for the 

 lupin, the coefficient lying^between 2 and 3 for a difference in 

 temperature of io° C. According to Lundegardh,* the res- 

 piratory curve falls into four regions : there is at first a gradual 

 increase with rising temperature from the minimum to the 

 first optimum at 40 C, in this phase Q 10 varies from 1-9 to 

 3-3 ; there next follows a rapid increase from 40 to 46 C. ; 

 the third phase is characterized by a marked increase to the 

 second optimum at 50 C. ; finally at temperatures above 

 50° there is a rapid fall in the respiration intensity. Lunde- 

 gardh explains the results obtained at temperatures above 

 40 C. on the assumption that at about this point the proto- 

 plasm enters into a more labile phase comparable to that of 

 a colloid whose viscosity suddenly changes at a high tempera- 

 ture. 



In passing, it may be mentioned that the maintenance 

 of a relatively high temperature is one of the factors which 

 is responsible for physiological diseases, e.g. blackheart in 



potato tuber.f 



With regard to low temperatures, it is a well-known fact 

 that seeds, lichens, mosses, etc., especially when dry, retain 

 their vitality on exposure to intense cold ; even so low a 

 temperature as — 250 C. will not cause death. Since res- 

 piration is in its complete expression a concomitant of life, 

 the process must continue in an attenuated form even at so 

 low a temperature as that of liquid air. 



FOOD. 



The continuance of respiration ultimately depends upon 

 adequate food supplies, and the intensity of respiration may 

 be much influenced by the presence of substances immediately 

 available as respirable material. Formerly it was considered 



* Lundegardh : " Biochem. Zeit.," 1924, I54» 195- 



f See, for example, Bennett and Bartholomew: "Univ. California 

 Publications," Technical Paper, No. 14, 1924- 



