14 



PLANT RESPIRATION 



to the group of decay fungi which grow well on proteins alone 

 {i.e. in the absence of carbohydrates). The intensity of the 

 bacterial light is sufficient to evoke the formation of chlorophyll 

 in etiolated plants.^ 



The nature of the phosphorescence consists in this — that in 

 the respiration of the phosphorescent plants there are formed 

 certain materials which glow after death and are designated as 

 luciferins. Their chemical nature is not yet established but it is 

 very probable that they are to be classed in the group of pro- 

 tein compounds- and are formed under the influence of specific 

 enzymes.^ Moreover, it is well-known that a few organic 

 compounds glow with slow oxidation. 



Various workers have endeavored to determine quantitatively 

 the respiratory energy used up by plants. It is enlightening 

 that the fraction of the total energy of respiration which is 

 not dispersed in the form of radiant energy but is used in the 

 protoplasm for various vital needs, may, under some conditions, 

 be moderately small. We know how insignificant is the eco- 

 nomic quotient [efficiency] of our steam engines and other 

 heat apparatus. The first calorimetric determinations were 

 carried out with resting organs;^ no wonder that in this case 

 the radiant energy produced by the respiration was practically 

 equal to the total heat of combustion of sugar. The following 

 table of Rodewald shows what quantity of heat corresponds to 

 the production of i cc. of CO-, or the absorption of i cc. of 

 oxygen. 



> Isatschenko, B. Abh. d. bot. Gartens in St. Petersburg 11 : 31, 44- IPH- 



-Dubois, R. Compt. rend. 111: ibi. 1890; 123: 653. 1896; 153: 690. igri; 165: 

 ii. 1917; 166: 578. 1918; Compt. rend, des seances de la soc. de biol. 81: 317. I9i8; 

 82 : 840. 1919. 



' Dubois, R. loc. cit.; Harvey, E. N. Amer. Jour. Physiol. 44: 449. 1916; 45= 3 18, 342. 

 349. 1917; J- Gen. Physiol. 5: 275- 1922-23. 



♦Rodewald. Jahrb. f. wiss. Bot. 18: 263. 1887; 19: 221. 1888; 20: 261. 1889. 



