Rothamsted Symposium on Trace Elements 



44 



In pot experiments with wheat growing in a copper-deficient 

 soil a relation between the copper and nitrogen nutrition of this 

 plant was found. Without an addition of copper, normal though 

 small plants were obtained when no nitrogen was added to the 

 soil. With the addition of increasing amounts of nitrogen in- 

 creasing amounts of copper had to be given in order to obtain 

 normal plant growth (Figure 4). 



■ I txxq of CuSCX /pot 



6.5 i:o i.o ao 3.0 



N H4 NOj adaea per pot. 5 



Textfigure 4.— Effect of increasing amounts of copper and nitrogen on 

 wheat grown in a copper-deficient soil. 



In experiments with microorganisms the essentiality of copper 

 for a number of biochemical reactions was shown. The oxidation 

 of ethyl alcohol to acetic acid by Acetohacter aceti was much stimu- 

 lated by minute amounts of copper as is seen in Figure 5. The 

 formation of the black pigment in the spores of As^per^llus niger 

 and of cultures of Azotohacter chroococcum requires copper. The 

 same is true of the oxidation of manganous compounds to manga- 

 nese dioxide by fungi. In these reactions copper apparently has 

 the function of an oxidation catalyst. 



