V. H. FREED 



Oregon State College 



F. J. REITHEL 



University of Oregon 



L. F. REMMERT 



Oregon State College 



Some Physical-Chemical Aspects of Synthetic 

 Auxins With Respect to Their Mode 



of Action 



It has become very apparent that the mechanism of action of synthetic 

 plant growth regulators and the relation of their chemical structure to 

 this activity is inextricably interwoven. Many attempts have been 

 made to relate structure of the compound to activity, or to afford an 

 explanation of the mechanism of action. Either case involved the 

 necessity of considering the other facet of these interrelated prob- 

 lems. Thus, in attempting to explain why the varying of the organic 

 structure of a synthetic plant growth regulator modifies its activity, it 

 became necessary to invoke a mechanism of action compatible with 

 the observations. 



Most of the work attempting to relate structure of synthetic growth 

 substances to their plant growth regulating activity has been from 

 the standpoint of the organic chemistry of these molecules (1, 9, 13, 17, 

 26) . It has been found that the number and kind of atoms in the 

 molecule as well as their arrangement in relation to each other are of 

 prime importance in determining whether or not the molecular spe- 

 cies will be active. However, it must be remembered that the physical 

 properties and geometry of the molecule are related to activity also. 

 This paper is concerned with an attempt to relate some physical 

 chemical aspects of synthetic plant growth substances to the biological 

 action of these chemicals. 



* Taken in part from a doctoral dissertation submitted to the Graduate School, 

 University of Oregon, by senior author. Also Technical Paper No. 1263, Oregon 

 Agricultural Experiment Station. 



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