306 Freed, Reithel, and Remjnert 



coal. lAA was very good, 2,4-D and 2,4,5-T were excellent, but when 

 we examined a whole series of chlorinated phenoxy acids the corre- 

 lation with growth activity was not good because the more you chlorin- 

 ate the more adsorption you get regardless of where the chlorine is 

 placed in the ring. Thus, 2,4-D and 3,5-D are of equal activity in this 

 adsorption system, 2,6-D shows a little less adsorption, but 2,6-D is 

 very much in the same class as 2,4-D. 2,4,6-T, and 2,3,6-T are less 

 adsorbed than the other trichlorinated ones but they were better 

 than 2,4-D. I think that it may have implications in some aspects of 

 auxin function in cells, but there's not a good correlation between 

 auxin activity and adsorption, in our system. 



Dr. Wain: I think it's a very important point that Dr. Leopold 

 raised. The compound with a ring system with more chlorine atoms 

 can in fact be absorbed and can act as a competitive antagonist. But 

 it's not necessarily a growth substance because other features of the 

 molecule are important. 



