THE INFLUENCE OF POST-RADIATION 

 FACTORS ON EFFECTS PRODUCED IN 



BARLEY 



L. Ehrenberg 



Institute of Organic Chemistry and Biochemistry, University, Stockholm 



As a background for the data to be given, attention is first called to the 

 properties of the barley plant as experimental object. In Figure 1 the fate 

 of a barley seed is summarized. The dry, dormant seed, which can be 

 stored for a definite time, germinates after sowing, giving rise to a seedling 



Post-irradiation influences 



Irradiation 



sowmsf 



I 



dnrmant 

 seed 



storage 



germma- 

 tion 



-^seedling- 



t 



4 



mature 

 " plant ' 



sexual I 

 reproduction | 

 >-2nd generation- 



t t 



later 

 generations 



t 



Secondary processes 



Observed 

 effects : 



Death 



Chromo- 

 somal dis- 

 turbances 



Growth 



inhibition 



Elimina- 

 tion of 

 genetic 

 changes 



Sterility Mutations Evolutionary 



effects 



Figure 1. Development of a barley seed, irradiated in the dormant state. Observed effects and possible 



post-irradiation influences 



and, after further growth, to a mature plant. By sexual reproduction the 

 latter gives rise to second generation seeds, which pass through the same 

 ontogenic cycle, and an unlimited number of later generations then follow. 

 In irradiation experiments designed to produce mutations^, any of these 

 developmental stages can be irradiated. In the present study dormant 

 seeds or seeds at a time just after the start of germination were irradiated. 



The (biological) observed effects registered at any moment after the 

 irradiation are due to the chemical changes produced at the moment of 

 irradiation (primary act) and to a series of secondary processes following the 

 primary act. These may be studied {a) by a variation of the conditions under 

 which the radiation is performed, and [b) by post-irradiation treatment at 

 different times. 



285 



