MINERAL NUTRITION OF FUNGI IS 



tives of each class of fungi show that the presence of zinc in nu- 

 trient media stimulates growth [Metz (1930)]. Alosher et al. 

 ( 1936) regard zinc as essential for the dermatophyte Trichophyton 

 inter digit ale. In comparing the growth of Aspergillus niger in 

 media lacking zinc with that in media containing zinc salts, Porges 

 (1932) noted that a scanty, thin, smooth pellicle develops when 

 zinc is lacking, whereas in its presence a heavy, wrinkled mat is 

 produced. Steinberg (1919) secured an increase of mycelial mat 

 of A. niger amounting to as much as 230,900%, the increases being 

 correlated with the quantity of zinc present as an impurity in the 

 salts; as he indicates (1934), increases of this magnitude can hardly 

 be interpreted as "stimulatory" effects. 



Zinc does not uniformly influence conidial production in the 

 same manner in all fungi. Roberg (1928) and Porges (1932) 

 found that zinc inhibits sporulation of A. niger. Zinc represses 

 sporulation of Trichoderma koningii but stimulates conidial pro- 

 duction by Fiisariwn oxyspornm [Niethammer (1938)]. 



Pigmentation in fungi, as modified by the presence of zinc, has 

 been considered by Bortels (1927), Roberg (1928), and Metz 

 (1930). Metz's experiments involved species of Aspergillus, 

 Penicillium, Fusarium, Macrosporium, and Botrytis. He found 

 that the growth in zinc-deficient cultures is abnormal in color. 

 The problem was further complicated, however, because, al- 

 though mycelial growth is dependent primarily on zinc and to a 

 lesser degree on iron and copper, it is essential that each of these 

 heavy metals be present to produce normal colors in a particular 

 fungus. 



The profound effect which zinc exercises on the growth and 

 sporulation of fungi is an index of the influence which this ele- 

 ment exerts on digestive and respiratory activities. That this 

 fact has long been appreciated is evident from the work of 

 Richards (1899) and Watterson (1904). 



The formation of organic acids as waste products in fungus 

 metabolism is briefly considered in Chapter 4, but emphasis is not 

 placed upon zinc as a modifying factor. Zinc has been shown to 

 prevent the accumulation of different acids in cultures. This ef- 

 fect has been demonstrated by Bortels (1927) and Wassiljew 

 (1935) with oxalic acid production by A. niger, by Bernhauer 

 (1928) and Chrzaszcz and Peyros (1935) with citric acid produc- 

 tion by the same fungus, by Lockwood, Ward, and May (1936) 



