i;i8 



RADIATION H1()I-0(;V 



vival curx cs thai Ikiac been rcpoiicd with \aiii)iis liiii;;!. ()ii I lie liasi.s of 

 tlio analysis carriod out with Nnirosjjora (Xorinaii, lUol ). the occurrence: 

 of hotli sigmoidal and exponential sur\i\al curves amonji; tlie funsi may 

 reflect dilTerenees in the number of inu-lei per spore. Exponential sur- 

 vival was obtained with uninucleate conidia of Neurospora, whereas 

 sigmoidal survival was correlated with a nnilt inucjeate condition (Atwood 



001 



1 2 3 4 5 6 7 



DOSE, quanta X cnn"2 x 10''^ 



Fig. 11-3. Inactivation of Neurospora conidia by ultraA'iolet radiation. Uninucleate 

 and multinucleate survival curves. Average number of nuclei per coiiidiuni: curve I, 

 1.0; curve II, 2.3; curve III, 4.2; curve IV, 5.9. {Norman, 1951.) 



and Norman, 1949; Norman, 1951). Figure 11-3 shows the survival 

 curves obtained by Norman with uni- and multinucleate conidia of 

 Neurospora. Similarly, the ploidy has been implicated as an important 

 factor in j^east. The ultraviolet survival curves in yeast are generally 

 sigmoidal, but those of haploids are of much lower order than those of 

 polyploids (Sarachek and Lucke, 1953; Caldas and Constantin, 1951; 

 Warshaw, 1952; Pomper, unpublished). 



Mutation frequency curves have been obtained with various fungi. 

 Trichophi/ton mcntagrophytcs (Hollaender and Emmons, 1941), Neuro- 

 spora crassa (Hollaender, Sansome, et al., 1945), Aspergillus terreus 



