Phenoxyacetic acids, Plant growth regulators

The work of many investigators soon showed it to be extremely widespread in plants, and it became clear that it was a fundamental plant hormone (e.g., reviews 530, 655a). Excessive production of indoleacetic acid by parasites is responsible for certain types of plant tumor (e.g., 948). The synthetic plant growth regulators, which are in general substituted phenoxyacetic acids, probably function as indoleacetic acid analogues. 

The earliest successful biological QSAR correlating plant growth regulating activity of X-phenoxyacetic acids utilized Hammett sigma constants for electronic effects and pi-constants for hydrophobicity. Pi (designated by lower case Tt) for the most common substituents was taken as the difference in the... 

Historically Hansch correlated the Hammett o constant and log (n-octanol-water partition coefficient) of phenoxyacetic acids with their plant growth regulator activity producing equation 1 ... 

Several organic acids known as plant growth regulators—cinnamic, naphtaleneacetic, P-naph-toxy acetic, phenoxyacetic, salicylic, tartaric acids, and lAA—were separated on barium sulfate-calcium sulfate coatings. Several solvents were applied in order to investigate their separation potential, and the sequence chloroform > ethyl acetate > distilled water > propanol > carbon tetrachloride was observed. 

With these compounds the carrrier of fungitoxicity, the dimethylthiocarbamate ion, could be introduced into the plant, but the antifungal activity of the compound in vitro is low. On the other hand, the compounds show growth-regulating properties similar to those of phenoxyacetic acid derivatives in vivo (Van der Kerk et... 

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