RESPIRATION 299 



To what extent the products of hydrolysis of fat are immediately 

 consumable, is also a matter which remains for further study. 



The nature of the food (fat or carbohydrate) which is being 

 used affects decidedly the respiratory quotient. During the respi- 

 ration of fatty seeds the respiratory quotient is extremely low. 

 Since the fats contain less oxygen than the carbohydrates in 

 proportion to the hydrogen present, they are more efficient energy 

 producers per gram of material and use more oxygen if they are 

 completely oxidized. The equation which represents the complete 

 oxidation of triolein is 03^03(0^330)3+8002 = 57C0 2 +52H 2 0, 

 which shows that for every 80 molecules of oxygen taken in only 

 57 molecules are released in the carbon dioxide. The respiratory 



57 



quotient is thus — or 0.71. 



80 



When these fatty seeds ripen, the oil is formed from carbohy- 

 drate with the release of oxygen which makes the quotient greater 

 than 1 at this season. Thus ripening poppy fruits have been 

 found by Godlewsky (1882) to have a respiratory quotient of 1.5. 



Light. — Light increases respiration as observed by Borodin 

 (1876), who exposed to the light leafy twigs which had been kept 

 in darkness. This may be explained on the basis that the light 

 affects the food supply, which is directly related to respiration as 

 noted above. This is supported by the fact that the same wave 

 lengths which increase photosynthesis also increase respiration. 

 Light may have a further influence in that it increases the temper- 

 ature. Bonnier and Mangin (1884) and Spoehr (1915) find, in 

 addition, a direct light effect which is independent of photosyn- 

 thesis and heat, since it is observed in heterotrophic plants under 

 constant temperature. The effect is very small, but Spoehr at- 

 tempted to explain it on the basis of the ionization of the air 

 by light, which might possibly accelerate the oxidative processes. 

 Middleton (1927) found that when barley plants were placed for 

 an hour in air ionized by polonium and then placed in normal air, 

 respiration was as much as 30% higher in the ionized air. Whimster 

 (1927) found with Pelargonium zonale an increase of as much as 

 85% in ionized air; and these effects were found to be due to the 

 ions themselves and not to the ozone produced. 



In exceptional cases, e. g., Spirogyra, respiration is increased 

 in the dark, owing probably to the fact that nuclear and cell divi- 

 sions occur mostly in the dark in this plant. It is seen, therefore, 



