Rothamsted Symposium on Trace Elements 82 



The salient point, in our opinion, is that it is possible, in short 

 time tests, to demonstrate an action of manganese, and this must 

 be regarded as showing a direct, positive influence on root develop- 

 ment. We believe that this method of studying growth behaviour 

 may prove of value for the location of the function of manganese, 

 and we plan to continue our studies by combining observations on 

 growth, wdth determinations of carbohydrate and nitrate metabo- 

 lism, in the presence of manganese. 



Points from Discussion of Pa'per hy Proj. Burstrom 



Dr. Mulder:— 



1) Do you think that in different tissues and organisms differ- 

 ent mechanisms of nitrate reduction existi' In As'pergillus niger 

 I could not show any influence of manganese on nitrate reduction. 



2) In an experiment with excised roots growth could be ob- 

 tained only when the nitrogen was nitrate. With ammonium 

 salts and asparagin no growth was possible. As a normal growth 

 in this experiment occurred only when the roots were swimming 

 on the surface of the nutrient solutions it looks as if nitrates have 

 the effect of an improved oxygen supply of the solution. 



Prof. Burstrom:— 



1) Your experience with As^pergillus tallies with Steinberg's. 

 As all results go at present we must assume that we have several 

 different mechanisms of nitrate assimilation. We know that there 

 must exist several kinds of respiration, so it is theoretically possible 

 that the same holds true of the nitrate reduction. 



2) Nobody has succeeded in growing excised roots with nitro- 

 gen given as ammonium as far as I am aware. Oxygen is certainly 

 an important factor in root cultures and you are quite right that 

 with nitrate we introduce a new oxidizing agent in the tissues, and 

 obtain a redox-system, which is lacking in ammonium cultures. 

 It appears, however, that the roots need oxygen even in the pres- 

 ence of nitrate. 



Dr. Erkama:— 



1) Can we presume that these interesting reactions you have 

 found in isolated roots, as well as the mechanism of the respiration 



