Rothamsted Symposium on Trace Elements 84 



higher plants can utihze nitrate as a source of oxygen for the 

 metabolism. 



Prof. Lavollay:— 



Dr. Arnon has underlined appropriately the fundamental dif- 

 ference which exists between nitrates and ammonium salts. The 

 first are sources of oxygen utilisable by the cell. In our experi- 

 ence of the physiological role of magnesium, we have now shown 

 that the mycelium of Aspergillus niger deficient in magnesium 

 synthesizes lactoflavine in important quantities, which is the index 

 of a diminution in true oxidation. The production of lactoflavine 

 is important when nitrogen is furnished in the form of an am- 

 monium salt, which to the contrary, is reduced when one offers 

 nitric nitrogen to mycelium. We see in this the proof that the 

 oxygen of nitrates is utilised for cellular oxidations which is besides 

 very evident. 



Prof. Burstrom:— 



Of course the oxygen of the nitrate is consumed in some kind 

 of oxidation, when nitrate is reduced. Thus nitrate reduction 

 must increase the respiration. This was shown in 1920. 



