W. D. JACKSON 



Some information of the amount of post-storage damage with increasing 

 time of post-storage has been obtained. Figure 7 shows the total damage, 



%0 



^ days pre -storage 

 1 A days post -storage 



Figure 5. Frequency of chromosome breaks per cell in seed after fourteen 



days' post-irradiation storage, irradiation and pre-storage in various 



oxygen-nitrogen mixtures ( 1 • 2 kr X irradiation) 



expressed as the proportion of damaged cells, after various intervals of post- 

 storage in air. From this it would appear that little increase is obtained after 

 10 to 14 days. The total damage expressed as mean number of chromosome 



O2— irradiation interaction 



Direct action irradiation effect 



20 



%0, 



1A days pre-storage 

 lA days post-storage 



Pre-strorage 

 ^02 effect 



100 



Figure 6. Partition of the total irradiation-oxygen damage shown in Figure 5 



breaks after no post-storage and after two and four weeks' post-storage in 

 nitrogen, 20 per cent oxygen in nitrogen, and pure oxygen is shown in 

 Figure 8. Again, the total damage in 20 per cent oxygen increases rapidly 



14 197 



