. The chemistry and mode of action of plant growth substances; proceedings of a symposium held at Wye College, University of London, July 1955. Plant regulators; Auxin; Growth (Plants). 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
. The chemistry and mode of action of plant growth substances; proceedings of a symposium held at Wye College, University of London, July 1955. Plant regulators; Auxin; Growth (Plants). 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 ~^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. Please note that these images are extracted from scanned page images th
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