9. Inorganic Nutrition 



and 

 Metabolism 



i 



-norganic sources of nitrogen have been discussed in 

 the preceding chapter; here we are concerned with the utilization of 

 other elements. Fungi have relatively large requirements for phos- 

 phorus, potassium, sulfur, and magnesium and much smaller but defi- 

 nite requirements for at least five micronutrients (trace elements, minor 

 elements). The known essential micronutrients are iron, zinc, copper, 

 manganese, and molybdenum. The calcium requirement of fungi, 

 if specific, is of the same order of magnitude as the micronutrient re- 

 quirement, whereas calcium is a major nutrient for higher plants. 

 Boron, required by green plants, is not known to be needed by fungi. 

 The possibility of other micronutrient requirements in fungi must also 

 be considered. Effects of sodium chloride have been assumed here to 

 be non-specific, although it has been shown that sodium is required 

 by Anabaena cylindrica (4). 



The history of investigations on the mineral nutrition of fungi is re- 

 viewed by Foster (57). Early studies were primarily nutritional in 

 nature and were severely hampered by methodological difficulties. 

 More recent nutritional studies owe much to the pioneering work of 

 R. A. Steinberg on both the techniques and the basic concepts of the 

 field. Interest at the present time is shifting toward the problem of 

 the metabolic function of the inorganic nutrients, with special atten- 

 tion to enzymatic processes in which metals play a role. A return to the 

 exploration of still unknown requirements should be possible as purer 



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