2l8 PHYSIOLOGY OF NUTRITION 



asparagin is being formed, and both of these processes are dependent upon 

 the assimilation of oxygen. 



Respiration is closely related to all of the other processes occurring in living 

 cells. The relation of fat and carbohydrate content to the respiration of 

 germinating seeds may serve as an illustration of this. Many studies agree in 

 showing that the germination of fatty seeds exhibits respiratory ratio values 

 that are exceptionally low. It is thus suggested that the germinal activity of 

 such seeds is connected with a fixation of oxygen. It has been pointed out 

 (page 191) that the loss during the germination of fatty seeds is made up only 

 of carbon and hydrogen, while the amount of oxygen in the seeds increases. 

 This becomes clear in connection with the fact that the respiration of these 

 seeds involves the oxidation of fats, whose oxygen content is much smaller 



CO 

 than that of carbohydrates. Therefore, the value of the ratio -q- must be 



markedly less than unity in this case. The complete oxidation of triolein may 

 be represented by the following equation: 



Carbon 

 Triolein Oxygen dioxide Water 



C3H5O3 (Ci 8 H 33 0) 3 + 8o0 2 = 57 CO2 + 52H 2 0. 



Here the value of the oxidation ratio is I -> which is less than unity. Polovtzov 1 



00 



has shown that fatty seeds germinating in cane-sugar solution produce a direct 

 oxidation of sugar, the respiratory ratio being equal to unity in this case. 



The gas exchange accompanying respiration in ripening fruits that have 

 oily seeds, after the fats have begun to accumulate, presents a very different 

 picture. The formation of oils from carbohydrates (the direct products of photo- 

 synthesis) is possible only with the elimination of the superfluous oxygen. Thus, 

 the rate of carbon dioxide production increases in these ripening fruits, without 

 any corresponding increase in the rate of oxygen absorption, and the value of the 

 respiratory ratio becomes greater than unity. An experiment with ripening 

 poppy fruits 2 showed a rate of oxygen absorption of 21.72 cc. while the COn-e- 

 sponding rate of carbon dioxide production was 32.62. Thus, -q— = 1.5, which 



is greater than unity. 



§5. Apparatus for Measuring Plant Respiration. 3 — In respiration studies it 

 is necessary to measure one or both of the gases involved. When the determina- 

 tion of the rate of elimination of carbon dioxide is sufficient, Pettenkoffer tubes 

 (Fig. 91) are serviceable. These are glass tubes about 1.5 cm. in diameter and 

 about a meter long, filled with titrated baryta water [preferably barium 

 hydroxide dissolved in an aqueous solution of barium chloride] and supported 

 in an oblique position. A water aspirator is used to produce a slow current of 



• Polovtsov, V., Etudes sur la respiration des plantes. M6m. Acad. Imp. Sci. St.-Petersbourg VIII, 

 12 7 : 1-69. 1902. 



2 Godlewski, Emil, Beitrage zur Kenntniss der Pflanzenathmung. Jahrb. wiss. Bot. 13 : 491-543- 

 1882. 



« Palladin, W. f and Kostytschew, S., Methoden zur Bestimmung der Athmung der Pflanzen. Abder- 



halden's Handbuch 3: 479-515- 1910. 



