Plant Growth Regulating Activity of 3-Indolylthioalkanoic Acids

Abstract

The plant growth-regulating activity of 3-indolylthioacetic acid and ß-(3-indolylthio)propionic acid has been assessed using etiolated pea stem segment and curvature tests with indolylacetic, indolylpropionic and indolylbutyric acids as standards for comparison.

The sulphur-containing compounds are significantly less active in these tests than analogues containing methylene in place of sulphur and attempts to rationalize these differences in terms of physicochemical properties of the compounds are described. The effect of the 3-substituent in indoles on the size of the fractional positive charge on the ring nitrogen has been measured by n.m.r. spectroscopy.