FIGURE 9. Comparison of the weights of pea seeds in controls 

 and in plants which received 250 r. 



one of the X-ray dosages used exerted a stimu- 

 lating effect and only doses of 8000 and 16,000 r 

 exerted a depressing effect on the growth and 

 development of the plants. This depressing effect 

 lowered the yield by 30% for a dose of 8000 r, 

 and by 63% for a dose of 16,000 r. 



For neither the dry nor the soaked seeds of 

 wheat were we able to find stimulating doses of 

 X rays. Since many authors pointed out that 

 sprouts were more sensitive than seeds, either 

 dry or wet, it became necessary for us to try out 

 the effect of radiation on sprouts. Seeds of wheat 

 were allowed to germinate on wet filter paper; 

 of the germinating seeds we picked out those 

 which had just begun to show the sprout. After 

 irradiation with doses of from 50 to 8000 r, the 

 seeds were planted under laboratory conditions in 

 three groups, 100 seeds per group. Shoots ap- 

 peared simultaneously in all dosages and in the 

 controls. Further observations of the develop- 

 ment of the plants and periodic measurements 

 showed that doses of 50, 100, and 200 r did not 

 affect the growth and development of the plants, 

 whose size remained equal to that of the controls. 

 With doses of 5000'* r it was possible to observe 

 a weak depressive effect. With doses of 1000, 

 2000, 8000, and especially 16,000 r it was possi- 

 ble to observe a strong depression of develop- 

 ment. Plants irradiated by other doses developed 

 identically with the controls. Phenological ob- 

 servations showed that plants which received a 



* Translator's note: [This is a mistake; it should 

 read 500]. 



dose of 1000 r began sending up secondary stalks 

 4 days later than the controls, and that they be- 

 gan to ripen 10 days later. By harvest time far 

 from all of the plants exposed to this dose had 

 ripened; the ears were small and many of the 

 seeds were underdeveloped. At harvest time the 

 height of the plants was measured, and the num- 

 ber of ears was counted for every plant for each 

 of the doses. Threshed grain was weighed sepa- 

 rately for each plant. The average data (height 

 of plants at harvest time, number of ears, and 

 weight of seeds are counted per single plant) 

 thus obtained are presented in Table 11. 



An analysis of this table shows that the height 

 of the plants remained unchanged despite the 

 action of rather high X-ray dosages (only doses 

 of 8000 and 16,000 r decreased it significantly). 

 Similarly, only the strongest of all the doses 

 applied, i. e. , 16,000 r, reduced the number of 

 ears to 2 from 3 which was the number found 

 on the controls and on all the plants which had 

 received smaller doses. The weight of the grain 

 per single plant began to decrease with the ap- 

 plication of 4000 r and fell to nearly a third 

 when 16,000 r were used. 



In comparing the action of radiation on dry, 

 soaked, and sprouted seeds of wheat it was es- 

 tablished that the latter are the most sensitive, 

 for doses of 1000 r had strong depressive effects 

 on them. Summarizing the investigations of the 

 effects of X rays on wheat seeds, we can see 

 that for this plant, in Afanas'eva's experiments, 

 stimulating dosages have not yet been found. 

 This does not mean, however, that we should 

 stop trying to find them. It is possible that 



24 



