GERMINATION OF LETTUCE SEED 205 



SUMMARY 



Gibberellic acid and kinetin have different temperature ranges of 

 activity for promoting germination of Grand Rapids lettuce seed over 

 similarly treated water controls. Kinetin was effective at high tempera- 

 tures where gibberellic acid was ineffective; gibberellic acid was effec- 

 tive at low temperatures where kinetin was ineffective. The apparent 

 interactions of combinations of gibberellic acid plus kinetin at different 

 temperatures rule out the possibility that these chemicals produce their 

 effects by influencing the same process (es) regulating germination. 



The different temperature ranges of activity of gibbereUic acid and 

 kinetin were used to nullify their effects on germination after a 12-hr 

 period at room temperature, during which time red and far-red light 

 treatments were applied. During the 12-hr period neither gibberellic 

 acid nor kinetin could reverse the far-red light inhibition of germina- 

 tion though red light could. Thus the actions of gibberellic acid, 

 kinetin, and red light on promoting lettuce seed germination were ex- 

 perimentally separated from one another. The effect of the red, far-red 

 photoreaction can not be explained in terms of its regulating endog- 

 enous levels of gibberellin-like or kinin-like substances. 



Acknowledgment 



We gratefully acknowledge the advice on statistical procedures given by 

 Dr. M. A. Kastenbaum of the Mathematics Panel of the Oak Ridge 

 National Laboratory. 



REFERENCES 



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Danckwardt-LUliestrom, C. 1957. Kinetin induced shoot formation from 

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Evenari, M., G. Neumann, and G. Stein. 1953. Factors modifying the influence 

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Hillman, W. S. 1957. Nonphotosynthetic light requirement in Lemna minor 

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Kahn, A., J. A. Goss. and D. E. Smith. 1957. Effect of gibberellin on germina- 

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