RESPIRATION AND FERMENTATION 



249 



This loss is due to respiration, which accompanies germination. 

 Respiration is essentially the oxidation of sugars to the end prod- 

 ucts, carbon dioxide and water. It may be expressed by the fol- 

 lowing general formula : 



C 6 Hi 2 6 + 60 2 -> 6CO2 + 6H 2 0. 



Considering its end products, this reaction is the re- 

 verse of photosynthesis, which has been represented in Art. 3 

 as follows: 



6CO2 + 6H 2 -> C 6 Hi 2 6 + 60 2 . 



10 



30 



20 

 Days 



Fig. 100. — The transformation of reserve substances during the germination of 

 vetch seeds (diagram after Prianishnikov) . 



Respiration is also an opposite process to that of photosyn- 

 thesis in respect to the energy involved. It has been shown that 

 in photosynthesis solar energy is utilized in the construction of car- 

 bohydrates. During physiological combustion of carbohydrates, 

 on the contrary, energy is liberated at a rate of 674 Cal. per gram- 

 molecule (180 g.) of glucose used. 



This liberation of energy is the essential feature of the respira- 

 tory process. For all its vital activities, growth, movement, and 



