Table 11 

 (based on Afanas'eva's data, 1934*) 



by changing external conditions (for example, 

 temperature) it will be possible to achieve 

 success. 



In any case, of the three plants subjected to 

 the action of X rays, our small laboratory ob- 

 tained a significant increase in yield with peas, 

 and a very large increase with rye. Besides 

 continuing to work with the irradiation of rye, 

 we have already planted half a hectare with 

 experimental rye seeds at one of the collective 

 farms of the Moscow Oblast. The results of 

 these experiments will be described in another 

 article. We shall only point out that on both the 

 initial development and yield X rays have exerted 

 a most beneficial effect. 



The investigations conducted in our laboratory 

 on changes in the development of plants due to 

 irradiation of rye, wheat, and pea seeds were 

 set up with the idea of avoiding the mistakes of 

 our predecessors. 



1) The seeds irradiated in our experiments 

 received exact doses of X rays carefully meas - 

 ured by expert physicists using dosimeters. 

 2) The amounts of radiant energy were gradually 

 increased in order to obtain the full curve of 

 stimulating dosages (i. e. , according to the 

 Arndt-Schultze Law). 3) A sufficiently large 

 number of seeds was used in the experiments 

 so that results would not be affected by individ- 

 ual fluctuations. 4) Whenever possible, similar 

 conditions of temperature and humidity were 

 maintained both during irradiation and while the 

 plants were growing. 5) Thorough phenological 

 observations were carried on during the course 

 of the entire development of the plants from the 

 moment of germination to complete ripening of 

 the seeds. The crop was carefully gathered 

 and analyzed. These observations showed that 

 stimulation during the first stages of develop- 

 ment does not coincide with an increase in yield, 

 at least for the most thoroughly investigated 

 object, i. e. , spring wheat. 6) Measurements 



were carried on [throughout development]. 

 There were measurements of the main root of 

 the sprouts, measurements of the plants on the 

 twenty -seventh day after planting, and measure- 

 ments of ears and stems at harvest time. 

 7) The seeds were weighed in such a manner 

 that the weights of healthy and of diseased 

 seeds could be obtained as well as the total 

 weight. In addition, all the seeds of a single 

 plant, selected for the exceptionally large size 

 of seeds, were weighed on a torsion scale, 

 grain by grain. 



As far as the individual crops are concerned, 

 our investigations have shown that rye is suffi- 

 ciently sensitive to X rays that experiments can 

 be set up with it and a whole series of questions 

 which are of interest to radiation biologists can 

 be answered. These experiments: 1) showed 

 the incontestable application of the Arndt- 

 Schultze Law to the action of X rays on plants, 

 at least on rye, since the measurement of young 

 plants on the twenty-seventh day after planting 

 gave a splendid growth curve; a small dose 

 (250 r) stimulated development, 500 and 750 r 

 produced still further development in the same 

 direction, until at 1000 r maximum stimulation 

 was achieved, after which the curve began to 

 drop; 2) confirmed the different sensitivity of 

 soaked seeds and sprouts; 3) showed that differ- 

 ences do not depend on the quality of the rays, 

 i. e. , hard or soft rays; 4) the effects of radia- 

 tion showed up in different ways depending on 

 the individuality of various plants, which 

 affected the number and weight of seeds, length 

 of the stems and ears, time of ripening, etc. 



Besides these purely technical conclusions, 

 we also were able to establish the stimulating 

 effect of X rays on rye. Plants which received 

 beneficial doses developed more quickly, had 

 broader leaves, and exhibited a deeper green 

 color than the control plants. The average 

 diameter of the rootlets followed the same 

 curve of growth as the other parts of the plants. 



25 



