Chapter 1 

 NUTRITION OF FUNGI 



Fungi are commonly regarded as unable to synthesize their own 

 food; that is to sav, they are not autotrophic. It is customary 

 therefore to consider them parasites and saprophytes; these group- 

 ings are based upon whether they secure their food from living 

 organisms or from dead and decaying plant or animal tissues. 

 Parasitic fungi may better be spoken of as paratrophic, and 

 saprophytic fungi as saprotrophic. A moment's contemplation 

 will reveal, however, that these terms too are quite arbitrary and 

 inadequate. For instance, experience has shown that certain fungi, 

 such as the Peronosporaceae, Erysiphaceae, and Uredinales, are 

 strictly paratrophic. Others— for instance, the Lycoperdales and 

 Phallales— are strictly saprotrophic, and between these extremes 

 all degrees of intergradation exist. In fact, such terminology be- 

 comes confusing, because many plant pathogens are paratrophic 

 during part of their annual cycle and saprotrophic during the 

 remainder. 



Concepts regarding the nutritional relationships of fungi that 

 underlie such terminology emphasize the fact that fungi lack 

 chlorophyll, and thereby the impression is inferentially fostered 

 that neither parasites nor saprophytes perform syntheses. As a 

 consequence the metabolic changes they induce are not properly 

 appreciated, and too little consideration is given to the determi- 

 nation of how both parasites and saprophytes effect not only 

 analyses (katabolism) but also syntheses (anabolism). 



In this discussion the term food is used herein in the broadest 

 sense. Any substance is regarded as food which serves as a 

 source of energy or is used for growth and repair or for the 

 various metabolic processes of the fungus. This usage implies 

 that both inorganic and organic materials play a role in the nutri- 

 tional requirements of fungi and in this sense constitute food. The 

 inherent implications in this usage of the term food permit dis- 



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