CALDECOTT AND NORTH: RADIO-SENSITIVITY OF SEEDS 



373 



Y- 1.9444 X 



— HYDRATED IN PRESENCE OF 2 



— HYDRATED IN PRESENCE OF N 2 



35 



DOSE OF X-RAYS (10 r units) 



Figure 5. — Relation of interchange frequency to dose when seeds are 

 hydrated in the presence of either oxygen or nitrogen immediately follow- 

 ing X-irradiation. 



1 1 1 1 



Y» 0.158 X 



HYDRATED IN PRESENCE OF 2 



HYDRATEO IN PRESENCE OF N 2 



5 10 



DOSE OF X RAYS (10* r units) 



15 



20 



Figure 6. — Relatioji of mutation frequency to dose when seeds are 

 hydrated in the presence of either oxygen or nitrogen immediately follow- 

 i?ig X-irradiation. 



