i02 effects of exposing seeds 



Summary 



Seeds were exposed to radium preparations in sealed glass tubes, 

 and of activities of 7,000, 10,000, and 1,500,000. Under the con- 

 ditions imposed, exposure to rays from all of these preparations was 

 followed by a retardation of growth, the amount of retardation vary- 

 ing directly with the activity of the preparation. 



When seeds of timothy grass {Poa -pratense) and alfalfa were 

 exposed to /9 and y rays during imbibition and subsequent stages of 

 germination, both germination and growth were retarded and the 

 plants were etiolated. Microscopic examination of the etiolated 

 plants showed that in some cases the plastids had apparently failed 

 to form chlorophyll, while in others the green chloroplastids 

 seemed to have been disorganized. Bean seeds placed in contact 

 with the coated rod («, /? and x '"^ys) during germination were also 

 retarded. When timothy grass seeds were exposed to radium of 

 weak activity (7,000 x) an initial retardation was followed by appar- 

 ent recovery after an interval of five days." At the end of this period 

 the exposed seeds averaged even taller than those of the control cul- 

 ture, though other conditions of growth had been practically identical. 



A similar recovery of growth vigor followed exposure of bean 

 seeds to the coated rod of 10,000 x , and of lupine seeds to the 

 coated rod of 25,000 x . These results suggest the establishment of 

 a condition of radium tonus^ in which the organism becomes ad- 

 justed to a certain intensity of radioactivity in its environment, and 

 th(? rays of preparations of this strength cease to act as a stimulus. 



Exposure of seeds to a preparation of radio-tellurium in a sealed 

 glass tube was followed by results similar in kind to those following 

 exposure to radium rays. The germination of fungus spores (Exp. 

 7) was also apparently less vigorous in radium cultures than 

 normally. 



In one case (Exp. 18) the germination of seeds of Lufinus albus 

 and the subsequent growth of the radicle was apparently accelerated 

 16 per cent, by placing a radium-coated rod of about 10,000 x in con- 

 tact with the seeds as they germinated in moist sphagnum. 



3. Effect on Growth of Exposing Soaked Seeds 

 The aim of the following experiments was to ascertain the effect 

 on germination and growth of exposing soaked seeds to the rays of 

 radium. 



