Table 30 



Average percentage of nuclear divisions after different doses 

 (based pn Afans'eva's data, 1938) 



Table 31 



Average percentage of various stages of nuclear division relative 



to the X-ray dose 

 (based on Afanas'yeva's data) [1938] 



Dose 

 (r) 



Control 



125 



250 



500 



750 



1,000 



2,000 



4,000 



8,000 



16, 000 



Percentage of All 

 Figures in Division 



5.67 

 4.53 

 4.67 

 4.58 

 4.37 

 4.69 

 3.90 

 3.91 

 3.29 

 3.33 



Percentage of 

 Prophases 



3.36 

 2.32 

 2.44 

 2.52 

 2.28 

 2.25 

 1.81 

 1.97 

 1.30 

 1.29 



Percentage of Meta- 



phases. Anaphases 



and Telophases 



2.31 

 2.21 

 2.23 

 2.06 

 2.09 

 2.44 

 2.09 

 1.94 

 1.99 

 2.04 



telophases taken together predominates. Thus, 

 under irradiation the number of mitoses de- 

 creases at the expense of the early stages. 



Parallel to the study of changes in the rate 

 of nuclear division, we investigated the effect 

 of X rays on the rate of growth. These 

 experiments have shown that the only apparent 

 effect of X rays on wheat seeds is a retarda- 

 tion of growth. A comparison of the nuclear 

 division rate with the decrease of growth indi- 

 cates that the latter can be, at least partially, 

 explained by the decrease in the nuclear division 

 rate. In addition, those doses which have the 

 most inhibitory effect on plant growth also 

 induce the greatest intracellular changes: for- 

 mation of micronuclei, multinuclear cells, 

 chromatin bridges, inclusions in the cytoplasm, 

 etc. 



As has already been pointed out in the first 

 chapter, stimulating doses of X rays have not 

 been established for wheat, neither were bene - 

 ficial intracellular changes, resulting from 

 radiation, established. This circumstance con - 

 firms the correctness of our hypothesis concern - 

 ing the relationship between intracellular changes 

 and the stimulation of growth, development, and 

 yield. 



Polyploidy. One of the problems posed in 

 our laboratory was how to obtain polyploid 

 plants of rye, wheat, and peas. In our first 

 papers dealing with the influence of X rays on 

 these plants we wrote: "The formation of tetra- 

 ploid and octoploid sectors cannot but affect the 

 formation of sex cells. " And actually in the 

 descendants of these plants we find seeds all of 

 whose sprouts have either all polyploid cells 



86 



