88 RESPIRATION 



evolution of carbon dioxide and proteins insoluble * in pepsin, 

 increase in amount. As development proceeds, the carbo- 

 hydrates, which originally were abundant, become depleted and 

 the decomposition of protein is less vigorous and may even 

 cease. Hence in the later stages of germination there is a 

 more vigorous respiration under conditions of low protein 

 content than in the early phases of germination when more 

 protein obtains. The proteins which disappear are those of 

 the reserve food, not those which are presumably members of 

 the protoplasmic complex and which show a direct relation to 

 the amount of carbon dioxide evolved. This is shown in the 

 following table which relates to wheat germinating at 20 to 

 21 C. and gives the ratio of the carbon dioxide evolved per 

 hour to the amount of protein unacted upon by pepsin : 



Age of Seedling CO 2 

 in Days. N 2 ' 



4 i'o6 



6 1-05 



7 i'i8 



9 i'i5 



Palladin found a similar ratio to obtain in other plants, 

 the following being some of the values obtained : 



Wheat seedlings 1-05, 1-15, 1-07, ri8 



Lupin seedlings 1*12 



Etiolated leaves of the broad bean after cultivation 



on sugar solution 1*10 



The differences between these observed ratios are not 

 considered to be significant by Palladin in view of the experi- 

 mental difficulties. From his observations he draws the 

 general conclusion that for a given temperature and with an 

 adequate amount of carbohydrate, the relation between the 

 quantity of carbon dioxide evolved by different plants in one 

 hour and the quantity of protein unacted upon by gastric 

 secretion, in vitro, is a constant. For a temperature of 19 to 

 20 C, CO 2 /N 2 =i'i. 



The amount of the protein referred to, as Kidd, West 

 and Briggs have pointed out, is a measure of the amount of 

 respiring cell matter. 



With regard to the fats, there is but little precise 

 information available from the point of view of respira- 

 tion. Their conversion to carbohydrate is one phase of 



* The solubility being determined in vitro, 



