NILAN AND KONZAK: MUTATION INDUCTION EFFICIENCY 



445 



Table 1. — Response of Irradiated Barley Seeds to Post-Radiation 



Heat-shock Treatment. 



80 Kr. 



100 Kr. 



Aberrations Dry seeds 



Moist seeds 



Dry seeds 



Moist seeds 



No No No No 



Shock shock Shock shock Shock shock Shock shock 



•Percentage of control. 

 tNot recorded. 



24). (See Figure 3.) The important new finding, however, is that these 

 chemicals produce very few gross chromosome aherrations of the 

 interchange type. (18, 24). (See Table 2.) 



Recently, it has been found that chromosome bridges and, less 

 frequently, fragments and bridges occur at anaphase I in M, plants 



Table 2. — Frequencies of Chromosome Interchanges in Shoot-tip Cells of Treated 



Seeds and in Pollen Mother Cells of Mi Plants Following Treatment of 



Barley Seeds with Diethyl Sulfate and Gamma Rays. 



Treatment 



Field 

 sur- 

 vival* 



Frag- Trans- 



Cells ments Bridges Spikes locations 

 scored per cell per cell scored observed 



•Percentage of control. 



tMore severe treatment with new, more purified chemical. 



