A Possible Source of Error in the Chemical Detection of Indolyl Acetic Acid in Plants

Abstract

DURING investigations on the growth substances of fruits of cacao and bananas (Musa spp.), it was of interest to find that a substance was present in seeded bananas which gave a pink colour with ferric chloride/perchloric acid or p-dimethyl amino-benz-aldehyde/hydrochloric acid, corresponding to the R _F of indolyl acetic acid and to the zone of bioassay using the wheat coleoptile straight-growth test. Subsequent experimentation showed that although the straight-growth response was probably due-to indolyl acetic acid, the colour reaction was not. The technique of extraction and bioassay was essentially similar to that of Bennet-Clark and Kefford¹ with some minor modifications. Duplicate samples of the acid fraction from seeded banana fruit extracts were developed by the descending method on Whatman's 3 MM or No. 1 chromatography paper in isopropanol/ammonia/water (10: 1: 1). Synthetic indolyl acetic acid was developed as a marker. One sample was bio-assayed by the wheat straight-growth test and the other sprayed with ferric chloride/perchloric acid (1 ml. 0.05 M ferric chloride + 50 ml. 5 per cent perchloric acid).