92 



MUTATION AND PLANT BREEDING 



1000 



500 - 



if) 



<£> 



I 



TT 



1 1 1 — I I I I I I 



SEPALS 



PETALS 



' i i i i i i 1 1 



_I_L 



.1 1.0 10.0 



DOSE RATE (r PER 20 HOUR DAY) 



Figure 12. — Somatic mutation rate in sepals and petals of chronically 

 irradiated Lilium testaceum. After Sparrow, Cuany, Miksche, and 

 Schairer (163). 



tions seems in doubt in higher plants, there is no corresponding doubt 

 about mutational events derived from chromosomal breakage and 

 rearrangement. The various kinds of such aberrations have been 

 outlined above (Section VI) and almost all of these have been identi- 

 fied with phenotypic changes of some type. For instance, duplications, 

 deletions, translocations, inversions, isochromosomes, and breakage- 

 fusion-bridge cycles have all been well documented elsewhere (16, 39. 



