2 3 8 



NUTRITIVE METABOLISM 



by means of the energy derived from this process are able to use 

 carbon dioxide of the air or that which has been in combination 

 with the ammonia in the construction of the carbohydrates. The 

 nitrate bacteria oxidize nitrous acid, and obtain energy from which 

 similar synthetic processes are made possible. 1 



305. Chemosynthesis of Nitrogenous Substances. Before the 

 carbohydrates formed by photosynthesis may be assimilated by 

 living substance they must be formed into 

 new compounds containing nitrogen, in 

 such manner as to constitute a proteid. 

 This combination is made between glucose, 

 or maltose,, on one hand and nitrates, or 

 ammonia on the other. The presence of 

 sulphates and phosphates is also neces- 

 sary, and the acids named are generally in 

 the form of salts of magnesium and potas- 

 sium. Calcium does not appear to take 

 any direct part in the process, yet it is 

 necessary to neutralize injurious bye-pro- 

 ducts. The synthesis of the proteids ap- 

 pears to take place most rapidly in cells 

 containing chloroplasts, in light, probably 

 because of the greater abundance of the 

 carbohydrate, although it may occur in 

 any part of the plant and is therefore a 

 chemosynthetic process. No other source of energy is available 

 to fungi by which it can be carried on. The nature of the first 

 product of the synthesis has not been determined, although sup- 

 posed by several investigators to be amides. In such instances 

 the end reaction might be expressed by the following formula : 



; 4 H 8 N 2 O s + K 2 C 2 4 + H 2 + Cy 



asparagin -f- potassium -+- water -)- oxy- 

 oxalate gen- 



The amide, asparagin, formed is diffusible and might be easily 



1 See literature list, Pfeffer. Plant Physiology, i : 361. 1900. 



"1 



Fig. 120. Service vessel 

 for mercury consisting of a 

 separatory funnel of a ca- 

 pacity of a liter, supported 

 by bent rod, with curved 

 end. 



