Doses of even 250 r have an inhibiting effect on 

 the development of rye; doses of 500 r produce 

 approximately the same effect. But when the 

 dose is increased to 750 r, some of the plants 

 develop poorly while the remainder die. A dose 

 of 1000 r has such a retarding effect on the 

 plants that they barely reach a height of 2 to 3 

 centimeters. With doses of 2000 r only a few 

 sprouts survived; with a dose of 4000 r only one 

 survived; while a dose of 8000 r was completely 

 lethal, not a single plant surviving. 



However, we did not limit ourselves to a 

 single optical evaluation. On the 27th day after 

 irradiation, i. e. , just before setting the plants 

 out in the field, we carefully measured them, 

 both the controls and those which had received 

 various dosages of radiation. The results of 

 these measurements can be seen in Table 2. 



A careful examination of this table will reveal 

 that a dose of 250 r is already sufficient to re- 

 tard the average height of the plants, but the 

 average bushiness is still somewhat higher than 

 in the controls. Besides, the differences be- 

 tween the effects of soft and hard rays begin to 

 show up here: the soft rays have a less drastic 

 effect on the plants. This difference also shows 

 up in other doses with the exception of the 750 r 

 dose, where the soft rays produce smaller size 

 and less bushiness than the hard rays. But, in 

 general, the difference between the effects of 

 soft and hard rays in our experiments was so 

 slight that in future presentation of data, we will 

 deal only with hard rays, since they were used 

 in the majority of experiments. 



The phenological observations conducted by 

 us in the spring and summer of 1932 demon- 

 strated that the average irradiated plant headed, 

 flowered, and ripened at about the same time as 

 the controls. However, individual variations 

 for some plants were 3 to 4 days. These indi- 

 vidual differences are frequently encountered 

 among irradiated plants, as we shall see when 

 we turn our attention to the study of other 

 aspects. 



We should note that only during flowering did 

 some of the irradiated plants attract attention 

 by their unusual development. Such plants could 

 be encountered only with dosages of up to 1000 r. 

 Starting with doses of 2000 r obviously degen- 

 erate forms with smaller ears began to show 

 up. When the rye was ripe, the plants were 

 collected individually, and the entire contents 

 were subjected to analysis. The number of 

 ears was counted, the total weight of seeds was 

 obtained, the total number of grains, and also 

 the number of healthy and injured seeds. These 

 results are presented in Table 3. 



All these data refer to a single plant. In 

 analyzing this table it turns out that a dose of 

 250 r more than doubles the number of ears, 

 and the quantity and weight of seeds. A dose 

 of 500 r has a much weaker effect, although the 

 number of ears, and the weight and number of 

 seeds still show a significant gain over the 

 controls. A dose of 750 r depresses the devel- 

 opment of ears and seeds, while a dose of 

 1000 r has a still more depressing effect. Plants 

 that received doses of 2000 and 4000 r perished 

 early in the spring. 



If we were to project curves on the basis of 

 these data, we would see first a sharp rise of 

 all quantitative factors and then their gradual 

 falling off. This points up our mistake in setting 

 up the experiment, since for irradiation of 

 sprouts we took too large an initial dose. 



Apparently, we should have begun with 

 smaller doses, perhaps as small as 50 r. It 

 is possible that smaller doses also would have 

 produced increases in yield and we would have 

 obtained a more normal curve. 



Our experiments with irradiation of rye 

 sprouts indicate how wrong it would have been 

 for us to limit our observations to the initial 

 stages of development (as the majority of authors 

 did with various plants) or take them only as far 

 as ear formation (as Long and Kersten did). 

 Comparing the two tables, we can see how the 



Table 3 

 (based on the data of Breslavets, Medvedeva, and Afanas'eva, 1935) 



16 



