The mode of growth action of some naphthoxy compounds 



ACTIVITY OF PURE 2-NAPHTHOXYACETIC ACID DERIVATIVES 



The following substances have been tested in addition to the unchlorinated 

 acid (I): l-chloro-2-naphthoxyacetic acid (II), 3-chloro-2-naphthoxyacetic 

 acid (III), and 1 : 3-dichloro-2-naphthoxyacetic acid (IV). 



HO 



I 



C Crl2 



o ^o 



CI o 



HO 



I 

 Cj — CHo 



II \ 



o ^o 



o 



\ 



CI 



I 



o 



CHfl 



C 



CH2 OH 

 O 



OH 



CI 



CI 



II 



III 



IV 



According to Jonsson's explanation, III should be an auxin like the 

 unchlorinated acid I, whereas II and IV should lack auxin activity owing to 

 steric hindrance caused by the insertion of chlorine in the 1 -position. 



300 



Figure 1. The irifliierice on the root cell 

 elongation of chlorinated 2-naphlhoxyacetic 

 acids (2-NOAA). On the ordinate cell 

 length in /i. 



200 



100- 



o E-NOAA 

 X 7-Cl- 

 • i-Cl- 

 *1:3-diZ\ 

 t Roofs dj/ng 



10-^ 



10-^ 



10- 



10-'* 

 M 



The effects on cell elongation are shown in Figure 1. It appears that with 

 the exception of the 3-chloro derivative, the acids slightly increase cell 

 elongation up to 3.10~^M, which is a non-auxinic effect shown by the 

 unchlorinated acids (Burstrom, 1955). Their behaviour, however, differs at 

 higher concentrations; thus, the 1 -chlorinated acid gives a considerable 

 increase in elongation, giving an activity curve resembling that of the root 

 auxin 1-naphthoxyacetic acid. The dichloro acid is practically inactive, 

 whereas the 3-chloro compound shows all usual signs of being an auxin. 



These observations are in good agreement with Jonsson's rules, under 

 which the 1- and 1 : 3-chlorinated acids should lack auxin activity. However, 

 it is impossible from this or any other rule to predict whether an acid lacking 

 auxin activity should possess some kind of antagonistic activity. In this 



135 



