of detail, and the multiplicity of aspects which 

 this author investigated place her in the first 

 ranks of X-ray biologists. In her first work, 

 which was devoted to research on sunflowers 

 (1926 and 1928), she compared the effects of 

 doses from 5 to 10 HED on dry and soaked seeds. 

 She studied the relationship between amounts 

 of exposure and growth; she investigated the 

 effects produced by radiation on catalysis, oxi- 

 dation, and respiration. Not satisfied with these 

 physiological investigations, she turned her 

 attention to phenological observations, which 

 gave most significant results with doses of 10 

 HED. Her experiments showed that germina- 

 tion of seeds is not accelerated by irradiation, 

 while sprouting is slightly retarded. Soaked 

 seeds irradiated with medium doses came to a 

 complete halt in their development in the first 

 3 weeks, after which there was a temporary 

 acceleration. The depression of growth during 

 the first 3 weeks as a result of irradiation is 

 approximately proportional to the dosage. 

 Plants grown from seeds soaked previous to 

 irradiation did not attain the size of the control 

 plants, but they bloomed earlier. In her next 

 work (1931) the author presented the results 

 obtained from irradiation of two thistles, sev- 

 eral Solanaceae and Vicia faba. In order to 

 give stimulation a chance to show its effects, 

 Johnson permitted her plants to grow for 25 

 days, since previous experiments demonstrated 

 that the effects of radiation tend to vanish 3 

 weeks after irradiation unless a second dose 

 is administered. Comparative examination of 

 fresh and dried weights of the irradiated and 

 control plants revealed that only one plant, 

 "sunberry, " had increased its weight due to 

 stimulation with weak doses of X rays. Since 

 one weak dose, in Johnson's experiments, did 

 not produce stimulation, she gave a second dose 

 after a certain interval. It is interesting that 

 in these experiments Johnson used the same 

 dose for Vicia faba as Patten and Wigoder, who 

 pointed to the increase in size of the plant as a 

 result of irradiation. Despite the fact that 

 identical conditions were maintained for irradi- 

 ation (seeds were used after being allowed to 

 germinate for 40 hours in water), Johnson 

 failed to observe any stimulation in the roots or 

 tubers. Irradiation of tulip bulbs caused the 

 leaves to lengthen, but left the formation of 

 flowers unaffected. In this work the author 

 presents her observations concerning the in- 

 crease in growth of plants by irradiation of 

 bulbs and tubers of certain plants. She points 

 out that when these experiments were set up 

 under more or less field conditions, they did 

 not exhibit the effects of stimulation. The 

 irradiation of wild potato tubers from Colorado 

 gave favorable results in the preliminary ex- 

 periments. However, this experiment was 

 given up when the author discovered that upon 

 repetition with a large number of samples, this 

 reaction could not be obtained. 



Finally, Johnson [1936c] wrote a long article 



in Duggar's book entitled The Biological Effect 

 of Radiation in which she summarized the re- 

 sults obtained by her, and others. Johnson 

 concluded that strong and medium doses of rays 

 have a harmful effect on the development of 

 plants. As for weak doses, she considers that 

 in the rare cases where they produced results, 

 the authors did not give sufficient consideration 

 to the individual variability of plants. 



Zankevich and Brunst ( 1937) were studying 

 the effects of X radiation on individual develop- 

 ments of tobacco [ Nicotiana rustica ], poppies, 

 flax, and rhubarb. Increasing doses of radia- 

 tion were used (250, 500, 750, 1500, 3000, 

 6000, and 10, 000 r). Doses of 500 and 750 r 

 had a stimulating effect on tobacco and flax. In 

 tobacco the increase in size was of transitory 

 nature, but in flax a certain amount of stimula- 

 tion was retained until the end of the growing 

 season. Medium doses of radiation resulted in 

 a retardation of growth, which was in degree 

 directly proportional to the dosage. Large 

 doses had a lethal effect. The authors make 

 an interesting observation to the effect that the 

 "latent period" of plants is of different dura- 

 tion: in poppies and flax it lasts 7 to 10 days, 

 while in tobacco and rhubarb it is of short 

 duration or entirely absent. 



Zaurov in 1937 used various doses of X rays 

 on the seeds of Indian hemp. He observed an 

 insignificant increase in length of stems with 

 a dose of 500 r in the first experiment and a 

 similar [insignificant] increase with a dose of 

 2000 r in a second experiment. Depression 

 set in starting with doses of 4000 r. Small 

 doses of X rays (125 to 1000 r) produce an 

 increase in bushiness; larger doses depress 

 bushiness. 



Breslavets and Sinitskaya (1937), who were 

 interested in changing the form of ornamental 

 plants, set out to study the effect of X rays on 

 these plants. They irradiated dry seeds, de- 

 spite indications from the literature that irradi- 

 ation of sprouting seeds is more effective. 

 This was done for a definite purpose: "If the 

 effect of some dose of X rays on dry seeds 

 were to cause a change of shape or coloring in 

 the leaves, flowers, or both, it would then be 

 possible to send the dry irradiated seeds to 

 various horticultural state farms and to ama- 

 teurs, while sprouted seeds could only be used 

 by us. " Summarizing the effect of X rays on 

 five kinds of ornamental plant seeds, the authors 

 concluded that it was not possible in a single 

 case to obtain the correct biological curve for 

 germination and sprouting power of the plants. 

 However, it is interesting to note that the ex- 

 periments brought out a differential sensitivity 

 to X rays of these plants. This result was to 

 be expected since the five plants belonged to 

 completely unrelated families. The most sensi- 

 tive to X rays turned out to be sweet peas; this 

 could have been foreseen on the basis of 



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