W. YEMM 



10 



Barley "Roots 



0.0025" M NH 4 H 2 P0 4 



Glutamine 



A 



ASPARAGINE 

 E3 



Ammonia 

 -O 



Other Amino 

 -A 



3o 



Figure 4. Changes of amino-acids and amides in excised barley 



roots during the assimilation of ammonia-N. Samples of 40 



root systems were analysed after varying periods of assimilation 



in aerated culture solutions containing ammonium phosphate. 



uj 20- 



5 10 



Hours. 



Figure 5. The incorporation of isotopic nitrogen into the nitrogenous 

 constituents of excised barley roots. Ammonium phosphate contain- 

 ing 29-3 atom per cent, excess 15 JV was supplied to the roots, and 

 the separated fractions subjected to analysis in a mass spectrometer. 



56 



