The mode of growth action of some naphthoxy compounds 



Table 1 



The influence of 3-indoleacetic acid {lAA) and oi-{3-indole) isobutyric acid {liBA) on the differential 



elongation in wheat roots 



Cell lengths in fi. The concentrations of lAA and I;BA have been chosen so that the 

 combination should give no change in the average elongation. 



to mention the bulk growth of an organ, is, of course, the sum of these two 

 different actions. It is not known, however, how these are related to the 

 elongation mechanisms. The ideal additive effect of the two compounds is 

 well shown in Table 1. 



That the inhibiting action of auxin is physiologically separated from the 

 positive actions of root auxins has been clearly supported by Rufelt (1954), 



Free (inactive) auxin 



Phasel 

 /lux in promoting 



Phases 

 Auxin inlii biting 



Auxins 

 3-NOAA 

 3-Z\,8-N0AA 



Roof auxins 

 {'anti -auxins') 

 liBA 

 t-Z\2-N0AA 

 and fnacf/ve 

 onfoffonisfs 

 1:3-diZ\^,E-N0AA 



(A = auxin i KB A = 3 -indole \i^butyric acid; 

 2-N0AA=2-napfithox^acetic acid with Z\-derivativesj 



Tentative diagram of the action of 2-naphthoxy derivatives. 



Figure 5. Suggested points of action of 3-indole and 2-naphthoxy compounds in the cell elongation 

 process proceeding in two phases {cf Figure 4). 



who has found that auxin and root auxin act on two different, previously 

 known and described geotropic systems in roots, which may or may not be 

 identical with the two modes of elongation. 



It can be tentatively assumed, at least as a basis for further discussions, 

 that the actions of the mentioned compounds are located as shown in Figure 5. 

 The root auxins of the z^fobutyric acid type exert growth action on the first 

 phase of the elongation, counteracted by their antagonists, which may be 



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