Table 26 



The average number of cells in the subepidermal layer. 

 (Based on Breslavets and Afanas'eva's data, 1937) 



UNEXPOSED 250 750 



2000 



8000r 



FIGURE 18. Changes in the number of cells in the second layer 

 of the root depending on the dose of X ray used (rye). 



single section (magnification 800X), thus deter- 

 mining the number of cells whose nuclei were 

 in any stage of mitosis. Table 27 indicates that 

 the number of mitoses at first increases, as the 

 X-ray dose is increased, reaching its maximum 

 at 750 r, after which the number drops (Figs. 

 19 and 20) (Table 27). 



Let us now turn our attention to the results 

 obtained when sizes of cells and nuclei were 

 measured (in cells we measured the length and 

 width, in nuclei we measured 2 diameters at 

 right angles to each other). 



From Table 28 we can see that the length and 

 width of cells does not change because of the 

 action of X rays, or rather, these changes are 

 so small that they can be disregarded. 



Thus, we can answer the question: on what 

 does an increase in root diameters depend? 

 Our counts and measurements indicate that it 

 depends on an increase in the number of cells, 

 whose size remains almost unchanged. 



Nuclei, however, show a certain increase in 

 size. Thus, Table 29 shows that the nuclei be- 

 come larger with doses of 250, 500, 750, and 

 1000 r. Since the size of the cells remains the 

 same, the relationship existing in normal roots 

 between the nucleus and the cytoplasm is upset. 

 And this explains the more accelerated cell 

 division when these doses of X rays are used. 



o 



LU 

 CO 



I 



CO 

 CO 



o 



O 



h- 



o 

 o 



CO 

 UJ 

 CO 



o 



o 



C) 



UNEXPOSED 250 



FIGURE 19. 

 per cross 

 on the 



Changes 

 sect ion 

 dose of 



750 



i n the 

 of the 

 X rays 



2000 



eooor 



number of mitoses 

 root depending 

 used (rye) . 



80 



