Table 13 

 (Based on Breslavets' data, 1942*) 



this we may draw the conclusion that Vester- 

 val'd rye grass is a radiosensitive plant. 



Meadow Grasses ( investigation of Afanas'eva) . 

 The seeds of the following meadow grasses were 

 subjected to X rays: bottom grasses — red 

 fescue, red top grass ( Agrostis ) and Kentucky 

 blue grass ( Poa pratensis) ; top grasses — fescue, 

 timothy, awnless brome grass, and American 

 slender wheat grass [ Agropyron pauciflorum ?]. 

 Doses of 750, 1500, and 3000 r were used for 

 irradiation. The irradiated and control seeds 

 were planted in boxes in quadruplicate. The 

 boxes were located in the greenhouse of the 

 botanical garden. Sprouts of the irradiated 

 seeds appeared at the same time as the sprouts 

 of the controls. The doses used had practically 

 no effect on the percentage of seeds germinating, 

 since we attached no significance to a small 

 rise in the percentage (3 to 6%). Then, the 

 second and third leaves were counted, but no 

 differences were observed here either. When 

 the plants were removed from the ground, the 

 number of leaves and roots of each plant were 

 counted, measurements of their length, weight, 

 and root -system circumference were made. 

 This was done for red fescue, meadow fescue. 



brome grass, and American slender wheat 

 grass. The data obtained failed to show any 

 differences, by any of the above signs, between 

 the irradiated and unirradiated plants. The 

 doses of X rays used produced neither a stimu- 

 lating nor a depressing effect. 



Data for the second scoring, at the time of 

 appearance of the third leaf, were obtained for 

 brome grass and fescue. These data show that 

 separate doses increase at this time the per- 

 centage of plants which have developed three 

 or more roots. This can be seen from the 

 following table (Table 14). 



From this table we can see that with a 

 dose of 3000 r the percentage of red fescue 

 plants having three or more roots is nearly 

 double that of the controls, namely: 70. 2% of 

 the plants (as against 35. 9%) have from 3 to 5 

 roots; while a dose of 1500 r increases the 

 number of roots in brome grass by 18% over 

 the controls. 



These data give us some background for 

 selection of doses which are capable of devel- 

 oping root systems. 



Table 14 



Percentage of plants which after 35 days have developed from 1 to 5 roots 

 (based on Afanas'eva' s data, 1943*) 



27 



