BRIEFER ARTICLES 



EFFECT OF ZINC AND IRON COMPARED WITH THAT OF 

 URANIUM AND COBALT ON GROWTH OF ASPERGILLUS 



It has been shown in a preceding publication 1 that treatment of 

 Pfeffer's nutrient solution with calcium carbonate at an elevated tempera- 

 ture removes from the solution the last traces of iron, zinc, and probably 

 the other heavy metals to a high degree. It has also been shown that 

 Pfeffer's solution so treated supports but a minimal growth of Asper- 

 gillus niger, but that the addition of both iron and zinc results in a phenom- 



grow 



The 



evidence presented, while showing that the presence of zinc in the cultural 

 solution is just as necessary for A. niger as the presence of iron, did not 

 include the action of other heavy metal salts. 



Theoretically the extension of these observations to include other 

 heavy metal salts is of importance, inasmuch as some light would be 

 thrown on the parts played by iron and zinc salts in the metabolism of 

 this fungus. If other heavy metal salts can replace either or both iron 

 and zinc salts, as is commonly stated, then iron and zinc are not essential 

 for the growth of A. niger and play the part of "chemical stimulants/' 

 If they cannot be replaced by other heavy metal salts, then they possess 

 properties that remove them from this category and place them among 

 the elements essential for the growth of A . niger. 



purpose 



Kahlbaum 



these were therefore used. The method used has already been described 

 (see footnote i). 



The results with Fe 2 (P0 4 ) 2 +4H 2 and with ZnS0 4 + 7H 2 apparently 

 point to an incomplete action of the treatment with calcium carbonate, 

 especially in reference to the removal of iron, since the cultures to which 

 only zinc was added gave dry weights much higher than usual (see foot- 

 note i). In the series containing both iron and zinc the usual phenome- 

 nal increases in dry weight occurred. Also regarding acidity it will be 

 noticed, what has already been pointed out, that a parallelism seems to 



'Steinberg, R. A., A study of some factors in the chemical stimulation of the 



pergillus niger. Amer. Jour. Bot. 6:330. 1919 



465] 



[Botanical Gazette, vol. 70 





