Table 33 



Increased frequency of mutation in Antirrhinum majus L. 



after irradiation of the male germ cells with short-wave radiation, 



independent of length of exposure or quality of rays. 



(based on Stubbe's data, 1937) 



Dose in 

 (r) 



3,000 

 6,000 



Irradiated 

 Male Germ Cells 



7,369 

 3,815 



Mutations 



237 

 176 



Percent of Mutations Resulting 

 from Irradiation 



1.38 -j_ 0.136 

 2.78 + 0.266 



two groups — group I received a dose of 30 r 

 and 3 hours later a dose of 450 r, group II 

 received 450 r directly. Measurements per- 

 formed 15 days later showed that the length of 

 the roots in group I was 50 millimeters, while 

 that of group II was 40 millimeters. In the 

 author's opinion, this result indicates that the 

 initial exposure to a weak dose of 30 r partly 

 protected the roots from the action of the large 

 dose and that this is a case of protection from 

 X rays by X rays, i. e. , the phenomenon of 

 radiophylaxis. This experiment was repeated 

 48 times and the same results were obtained 

 each time. 



The experiments of Glocker, Hayer, and 

 Jifngling were extremely interesting for their 

 time (1929). From a theoretical point of view, 

 write the authors, by analogy with the physical 

 action of X rays, it was to be expected that the 

 biological effect would be independent of the 

 quality of the rays since soft and hard X rays 

 have identical effect on ionization of air. The 

 experiment was performed with seeds of the 

 widely known Vicia faba equina. During the 

 year, 174 groups of 8 to 10 beans each were 

 subjected to the action of hard and soft X rays. 

 The qualitative data for the entire series were 

 identical: with small doses of up to 280 r soft 

 rays turned out to be more injurious, with 

 larger doses the difference tended to diminish. 

 Thus, with doses of 380 r, the effect of hard 

 and soft rays was identical, thereby confirm- 

 ing, in general, the biological sameness of soft 

 and hard rays. 



Doroshenko (1929-1930) writes that when 

 seedlings are irradiated, weak currents used 

 for a comparatively long period of time have 

 the greatest stimulating effect. High voltage 

 currents, even when used briefly, have an 

 inhibiting effect. Two small doses have a 

 greater stimulating effect than a single large 

 dose. 



Long and Kersten [1936] also point out that 

 greater stimulation is obtained with filters than 



without them. The filters used in the experi- 

 ment decrease the intensity of rays of all wave 

 lengths, but especially that of the soft rays, so 

 that if a stimulating effect is obtained it must 

 be ascribed to the action of the long wave part 

 of the spectrum, whereas an injurious effect is 

 to be ascribed to short waves. Or the stimu- 

 lating effect can be ascribed to the lesser inten- 

 sity and the injurious effect to the greater, 

 regardless of the wave length. Since the authors 

 felt the lack of data relating to the use of soft 

 rays on large amounts of dry seeds, they set 

 up an experiment in which dry soya seeds were 

 irradiated only by the soft part of the spectrum. 

 Since soft rays are absorbed by air, it was 

 necessary to place the seeds close to the [X-ray] 

 tube. For this reason the authors used the kind 

 of apparatus that held the soya seeds under the 

 X-ray machine for only 5 seconds, after which 

 they were ejected into vessels placed below; 

 then a second batch of seeds took their place, 

 and so on. Larger doses were obtained by 

 increasing the exposure time from 5 to 25 sec- 

 onds. When the voltage was increased, the 

 intensity of the wave length, and hence of the 

 whole beam, increased proportionately to the 

 square of the voltage used. The results of the 

 experiments were rather inconclusive. 



Stubbe (1937 and 1939*) considers that the 

 question of the relationship between the quantity 

 of the rays and the frequency of mutations should 

 be broken down into two questions: 1) what qual- 

 ities of the rays in general can cause mutations, 

 and 2) do equal amounts of rays of different 

 qualities produce equal increases in the fre- 

 quency of mutations? 



Stadler's numerous experiments with the 

 seeds of agricultural plants indicated that many 

 mutations can be obtained by X rays of medium 

 hardness as well as by hard rays of radium. 

 His and Stubbe's experiments with very soft 

 rays (Grenz rays), using 8 to 10 kilovolts, were 

 equally successful. 



Very hard X rays (500 kv) were successfully 



98 



