808 



BIOLOGICAL EFFECTS OF RADIATION 



pounds in darkness favorable to the germination of some crops of 

 Epilohium and indifferent to others. N compounds evidently are far 

 less effective substitutes for light with the germination of Epilohium 

 seeds than with Ranunculus sceleratus and Chloris ciliata achenes, while 

 acids as such have little action on any of them. Lehmann and Otten- 

 walder (68) found that dilute solutions of pepsin, papayotin, and 

 asparagin favored germination of E. hirsutum seeds in darkness, and 

 Niethammer (74) that dilute acetaldehyde solutions had a slightly 

 stimulative effect on E. parviflorum seeds. 



Using an Osram lamp as a hght source at 25°C., Ottenwalder (81) 

 exposed imbibed E. hirsutum seeds to light and then placed them in 

 darkness (see Table 7). 



Table 7 



Light intensity 



70 H. K. light 

 150 H. K. hght 

 300 H. K. hght 



Germination percentages 



96 hr. exposure 



59 



66 

 81.5 



72 hr. 



49 



61.5 



74 



48 hr. 



30.5 

 38.5 

 50 



Germination rose as the intensity and duration of illumination increased. 

 Even light of Moo H. K. for 95 hr. increased germination noticeably. 

 The higher the constant temperature, the less light was needed to force 

 germination. Fassbender (16) also found that the effectiveness of light 

 increased with the intensity, and that a period in a dark germinator 

 induced a "dunkelhart" condition. 



According to Kinzel, seeds of species of Epilohium proved to be light- 

 obligates at low temperatures and in the non-after-ripened condition. 

 He (49) showed that white light and the less refrangible half of the 

 spectrum were very effective in forcing the germination of E. angusti- 

 folium, but that blue light was less favorable than darkness. In E. 

 roseum blue light was superior to darkness. 



Lehmann (63) concluded that since proteolytic enzymes, acids, light, 

 and high temperatures acted on Epilohium seeds in the same way, they 

 must induce hydrolysis of storage proteins, and their action must be 

 catalytic. This conclusion, however, is merely hypothetical, for Leh- 

 mann did not show that the proteolytic enzymes actually entered the 

 seeds or that the other effective agents increased the hydrolysis of 

 proteins. 



According to Kinzel (51, Suppl. I, page 48) Oenothera biennis seeds 

 gathered cither half-ripe or ripe gave 100 per cent germination in light 

 after 9 months at 20°C. and no germination in darkness. Ripe seeds of 

 0. muricata (51, Suppl. II, page 39) behaved similarly. Takiguti (93) 



