RADIATION STUDIES ON FUNGI 



433 



in natural and laboratory cultures and many of the induced changes 

 resemble those already seen in nature, a fact appreciated very early by 

 investigators of fungi (e.g., Nadson and Philippov, 1932). This reflects 

 the nonspecific character of the action of radiation and radiomimetic 

 chemicals which typically increase the incidence of many different kinds 

 of mutations simultaneously. 



It is reasonable to suppose that there must be many separate effects of 

 radiation which pass unnoticed because the means for detecting them are 

 lacking. Some of these may be biologically unimportant, w^hereas others 

 may provide the underlying basis for some of the major observed results. 

 For example, the number and character of the lethal effects are not 

 known, although there is reason to suspect that many alternatives are 

 involved. It will often be difficult to find adequate criteria to distinguish 

 between primary effects of radiation and the secondary consequences of 

 cell morbidity, a ubiquitous problem in radiation biology. 



ULTRAVIOLET RADIATION 



Several recent articles are available on general biophysical aspects of 

 ultraviolet radiation, an agent which has been wddely used in experiments 

 with fungi (Loofbourow, 1948; Giese, 1945, 1950; McLaren, 1949). 

 Effects of ultraviolet on growth and respiration have been noted in yeasts 

 and molds, as shown in Table 11-2. 



Table 11-2. Some Nongenetic Effects of Ultraviolet Irradiation 



OF Fungi 



Stimulation by slight doses has been reported with various yeasts 

 {Saccharomyces cerevisiae, Saccharomyces ellipsoideus, Nadsonia fulvescens, 

 Zygosaccharomyces priorianus) and molds (Mucor genevensis, Mucor 

 guilliermondi) , based on increased growth on plates exposed to a graded 

 amount of radiation (Nadson and Philippov, 1928a). The interpretation 

 of such experiments is made uncertain by the possibility that stimulation 

 is brought about by substances released from the few killed colls. 



