CALDECOTT AND NORTH: RADIO-SENSITIVITY OF SEEDS 



375 



o 



CE 



»- 



z 

 o 

 o 



u. 

 o 



X 

 <£ 



UJ 

 X 



z 



_) 



Q 

 UJ 

 UJ 

 (/> 



15 



25 35 45 55 



DOSE OF RAYS (r Units) x I0 3 



65 



Figure 7. — Protection from X-irradiation by pre-heat treatment. 



irradiation heat treatment results in a reduction in the radiosensitiv- 

 ity of seeds. The logical next step was to determine whether or not 

 pre-irradiation heat had any influence on post-irradiation sensitivity 

 to storage. To determine this the following study was conducted. 

 Seeds were subjected to a temperature of 75° C for 24 hours and then 

 irradiated with a dose of 15,000 r. After irradiation, different segments 

 of the population were stored at room temperature for periods rang- 

 ing from to 48 hours before being hydrated either aerobically or 

 anaerobically. Six days after hydration seedling height data were 

 obtained and compared with data obtained from populations treated 

 in precisely the same way except that they were not subjected to the 

 pre-irradiation temperature treatment. The data presented compare 

 only the two extremes of the post-irradiation storage period, and 

 48 hours, because they illustrate the points of concern (Figures 

 8,9, 10). 



The following conclusions can be drawn from the data in this 

 experiment. First, that under conditions of either aerobic hydration 



