448 



PLANT GROWTH SUBSTANCES 



Perhaps of equal importance and interest, investigations with various 

 fungi have led to the experimental verification of the genetic basis of the 

 losses in synthetic capacity which in evolution may have led to require- 

 ments for exogenous supplies of essential metabolites. Work in this field, 

 initiated with the ascomycete Neurospora crassa (6), has been extended 

 during the past several years to a considerable number of other fungi. 

 Mutant strains of a number of fungi deficient in the synthesis of vitamins, 

 amino acids (as listed in Table i), and nucleic acid constituents, have 

 been produced by treatment with a variety of mutagenic agents in- 

 cluding radiation, mustard gas, and other chemicals. With the exception 

 of the imperfect fungus PeniciUium and the phycomycete Absidia glauca, 

 convincing genetic evidence has been obtained that the growth factor 



TABLE 1 

 Requirements of induced mutant strains of fungi 



Organism 



Vitamin 

 requirements 



Amino acid 

 requirements 



Mutagens used 



AND reference 



Neurospora all but B2, choline, all but alanine, X-ray (7, 45, 81) 



biotin* hydroxyproline Ultraviolet (7, 81) 



S-mustard (39) 

 N-mustard (48, 52, 

 81) 

 Ophiostoma all but B2, choline, for argmine. X-ray (25) 



thiamin,* Be* lysine, methionine N-mustard (24) 



Caffeine (26) 

 Glornerella for nicotinic. Be for tryptophan, 



Ivsine 

 Penicillimn all but pantothenic, all but alanine, 



Ultraviolet (51) 



X-ray, ultraviolet 



00 



N-mustard (35) 



Absidia 

 Ustilago 



for pantothenic, 



PAB 



for Bi, nicotinic 



B2 hydroxyproline, 



serine, glycine, 



threonine, tyrosine 



for histidine, 



lysine, tryptophan 



for arginine, 



isoleucine, 



methionine 



for lysine, 

 PAB, *pantothenic,*leucine, methionine. Ultraviolet (62) 

 biotin* phenylalanine, histi- 



dine, tryptophan 

 Coprinus for cystine, N-mustard (23) 



methionine 



Saccharomyces for nicotinic, Bi, 



Ultraviolet (29) 

 Ultraviolet (59) 



N-mustard (64) 



* Requirement of parental stock. 



