12 PLANT RESPIRATION 



respiration is not settled by them since the continual hydrolytic 

 processes evoke appreciable but unexplored fluctuations of 

 water formation." Experimental studies of water formation are 

 rendered dillficult by reason of the complicated methods and 

 manifold sources of error; in spite of this there is an urgent need 

 to remedy such a serious omission. 



3. PRODUCTION OF RADIANT ENERGY IN PLANT 

 RESPIRATION 



Plant respiration, like all slow combustions, involves a pro- 

 duction of heat. The amount of heat depends upon the given 

 respiratory material. Since in plant respiration carbohydrate 

 serves for the most part as direct material for combustion, we 

 may select as the point of departure for theoretical considera- 

 tions the heat of combustion of i molecule of grape sugar. This 

 amounts to 674 Calories.^ It was pointed out above that we 



may assume a direct oxidation of sugar only when -j^ is 



exactly i as shown by the gas analysis. 



Plants provide no thermo-regulatory contrivances. For 

 that reason the temperature of the plant body is for the most 

 part hardly different from that of the surrounding medium. 

 Thus, at first sight, it appears that plant respiration produces 

 no heat. In some cases in which moderately large plant organs 

 evince a considerable respiratory process, a direct increase in 

 temperature is at once perceptible.'- Thus a direct measure- 

 ment of temperature shows that in the Cereus flowers between 

 the filaments there is a temperature rise of 1.2"^.^ In the flowers 

 of Victoria regia a temperature increase of 12.5° was observed,^ 

 in flower spadices of Arum italicum — a rise of 36°. The tem- 



' Stohmann, F. Jour. f. prakt. Chem. 19: 115. 1879; 31: 273. 1885; Zeitschr. f. Biol. 

 13 : 364- 1894. [See also the editorial note on page 2.] 



= de Saussure. Ann. sci. nat. 21: 285. 1822; Ann. de chim. et de physique (II) 21: 

 279. 1822; Dutrochet. Compt. rend. 8: 741. 1839; 9: 613. 1839; Ann. sci. nat. (II) 

 13: I. 1840; and others. 



■^ Leick, E. Ber. d. V^ot. Ges. 33: 518. 1915; 34: 14. 1916. 



* Knoch, E. Untersuch. liber die Morphologie und Biol, der Blute von Victoria regia. 

 P. 38. 1897. 



" A strong proof of the existence of such hydrolytic processes resulted from 

 Bonnier's studies of heat production during seed germination (Bonnier, G. 

 Ann. sci. nat. de Bot. (VII) 18: 1-35. 1893).— EJ. 



