i/';;v 







■■■■ ;•-•.?:>. ^<- -//■ 



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FIGURE 16. Intracellular changes with a dose of 750 r: 



1) an abnormally large cell with two nucleoli; 2) the same with a 

 single nucleolus; 3) four nucleoli in the nucleus of a tetraploid cell; 

 W) the fusion of two long nucleoli, each of which was in turn formed by 

 the fusion of two nucleoli; 5) and 6) complex shapes of fused nucleoli; 

 7) nuclei passing from one cell to another (rye). 



As has been pointed out in the literature 

 more than once, soaked seeds have a completely 

 different sensitivity to X rays than sprouts. 

 When a dose of 5000 r is used on sprouts, the 

 growth and development of young plants is in- 

 hibited whereas the same dose used on seeds 

 stimulates their development and increases the 

 yield. A dose of 750 r has a still greater effect, 

 promoting the maximum yield in rye. Parallel 

 intracellular changes take place in the roots. 

 When this dose was used, two roots were found 

 to consist entirely of hexaploid cells, i. e. , the 

 number of chromosomes was triple that of nor- 

 mal diploid nuclei, which have 14 chromosomes. 

 Each nuclear plate had 42 chromosomes. We 



never encountered cells with a diploid number 

 of chromosomes in these two roots. On the 

 basis of these considerations we assumed that 

 these roots belonged to one or two hexaploid 

 plants. We do not know which because at that 

 time we did not make individual fixations. 



Following all three doses (250, 500, and 

 750 r), we almost never found changes which 

 could be considered detrimental to cellular 

 activity. Such changes appear only with a dose 

 of 1000 r and then in very insignificant amounts. 

 But as the dose is increased, the number of 

 changes increases, reaching its maximum with 

 8000 r. 



78 



