274 PHYSIOLOGY OF NUTRITION. 



20 C. 80 mgr. of C0 2 every two hours. If the plant is only to 

 be examined off and on as to its production of Carbon dioxide, 

 air must always be led through the food solution in the interval, 

 so that the roots may not suffer from lack of Oxygen. 



104. The Production of Carbon Dioxide in Intramolecular 

 Kespiration. 



The Carbon dioxide production in intramolecular respiration is 

 determined in the manner given below. Usually the quantity of 

 Carbon dioxide produced intramolecularly is far less than that 

 formed under similar conditions in normal respiration. In some 



cases, however (e.g. in seedlings of Vicia Faba), the ratio ^ i & 



equal to 1. Naturally, in comparative experiments on normal and 

 intramolecular respiration, we must use material in the same 

 state of development, if, e.g. it is required to determine the 

 influence of temperature on respiration. It is best to make several 

 comparative experiments one after the other with the same 

 material. At low temperatures plants do not suffer injury if 

 exposed to Hydrogen for a considerable time (many hours), and 

 they subsequently produce, when once more respiring normally, 

 as much Carbon dioxide as before the commencement of intra- 

 molecular respiration (see the investigations of Amm in his cited 

 treatise). At high temperatures (from 30 or 35 C. upwards) 

 the plants soon suffer, if kept too long in the Hydrogen ; the 

 experiments, therefore, must be continued for a few hours only. 

 The results of the experiments may be represented graphically. 

 Fig. 99 shows that seedlings of Lupinus (four or five days old) 

 always produce much less C 2 in intramolecular respiration than 

 in normal respiration. The optimum temperature for both kinds 

 of respiration lies at 40 C.* 



Intramolecular respiration takes place even when plants are 

 introduced into a vacuum. 



* This latter result, first determined by Amm, was confirmed by Chudiakow 

 (Lanchvirthschl. Jahrbilcher, Bd. 23). He disputes, however, the accuracy of 



some conclusions of Amm and myself. We had found that the ratio is not 



the same at all temperatures, and this statement Chudiakow, on the ground of 

 the results of his investigations, controverts. His work, however, is not, to 

 my mind, conclusive, and further researches are necessary to settle the matter. 



