Studies on plant growth‐regulating substances: XXXIII. The influence of ring substituents on the plant growth‐regulating activity of phenylacetic acid

Abstract

SUMMARYA comprehensive range of phenylacetic acids substituted with nitro, halogen, methyl, amino, hydroxyl and N‐acetylamino groups have been synthesized and their growth‐regulating activities assessed in the wheat cylinder, pea curvature and pea segment tests. The influence of substituents on molecular shape is shown to be more important in determining activity than their effects on electron distribution.Studies with 2,6‐disubstituted phenylacetic acids have indicated that the most active compounds can attain a certain spatial configuration in which one surface of the molecule, including the plane of the ring system, is flat and the carboxyl group is above with its axis of rotation perpendicular to this surface.Positional requirements for growth‐regulating activity in phenylacetic acids are shown to be less important than in the phenoxyacetic and benzoic acids.

The Physiological Significance of Phenylacetic Acid in Abscising Cotton Cotyledons

“…Generally, PAA was effective only when supplied at concentrations of 0.1 mm or more. This observation is in agreement with data presented by others using other assay systems (4,15). Treatment of leafless explants with PAA results in the partial suppression of petiole abscission and also reduces the increase in ethylene production normally observed as these explants age (Fig.…”

“…After 48 h only the ortho derivative still exhibited biological activity. Interestingly, this same hierarchy ofbiological activity has been observed by others using different assay systems (4).…”

Comparison of the Growth Promoting Activities and Toxicities of Various Auxin Analogs on Cells Derived from Wild Type and a Nonrooting Mutant of Tobacco

“…As expected from previous studies (9,19), only halogenated phenylacetic acids displayed significant growth stimulating properties (Table II). Among those molecules phenylacetic acids halogenated in the meta position, and to a lesser extent in the ortho position, were able to stimulate cell proliferation (Table II and Fig.…”

“…The halogen derivatives are apparently the best adapted to the active biological site as observed previously (9,16,19). Substitution in the ortho position is highly unfavorable as a result ofthe electric field effect of the substituent (10) and the considerable conformational interaction it induces on the acid function 13. p-Bromophenylacetic acid 7 has no auxin effect.…”

Ligand Specificity of Bean Leaf Soluble Auxin-binding Protein

“…Benzisothiazoles, synthesized by the procedures by Davis et al (13) (Table III). The m-and o-isomers of nitrophenylacetic acid are auxins but p-nitrophenylacetic acid is inactive as an auxin (3,9) and thus the ligand specificity of ABP qualitatively correlates with the biological activity of these phenylacetic acid derivatives. Inhibition of IAA Binding by Auxin and Antiauxin Phenoxya- (Table IV).…”