The Growth Substances separated from Plant Extracts by Chromatography. I

Abstract

SUMMARY Methods for the chromatographic separation on paper of indole compounds and for the direct biological assay of the chromatograms using the Avena cole optile straight-growth method are described. Reagents for the detection of the indole-3-carboxylic acids, indole-3-acetonitrile, and gramine as coloured spots on chromatograms are compared and the areas of such spots are shown to be pro portional to the logarithms of the quantities of substance present. The procedure of chromatography described is shown not to involve a loss of indole-3-acetic acid activity if chromatography is done in darkness and chromato grams are not stored in light and air. Methods are described for the extraction of growth substances from plant materials, the purification and chromatography, on paper, of the extracts and the bioassay of the chromatograms using Avena coleoptile sections. The ether extracts, containing acidic substances, of etiolated broad bean and pea shoots and roots, etiolated sunflower shoots, maize roots, and potato etiolated shoots and tuber have been chromatographed and the chromatograms bioassayed. On all chromatograms three areas active in Avena coleoptile section growth are found. One area of growth promotion is shown due to indole-3-acetic acid [IAA], Another area of growth promotion and one of growth inhibition are due to unknown substances, which are named accelerator a (a) and inhibitor (fi) respectively. On chromatograms of potato tuber a fourth growth-promoting area, in addition to those described above, is detected and is shown to be probably due to indole 3-acetonitrile [IAN], IAN or indole-3-pyruvic ac'd may occur together with IAA on chromatograms of extracts of immature maize kernels and cauliflower head respectively. On cabbage extract chromatograms the growth-promoting activity correspond ing in position with IAA is shown to be due to IAA and to IAA alone. In etiolated broad bean shoots IAA is the predominating growth substance in the stem and /3 predominates in the first lateral bud. The latter is suggested as an explanation of apical dominance, and the predominance of j8 in potato tuber skin is suggested as an explanation of dormancy in tubers. In the broad bean root the acidic growth-substance patterns, for the whole root and for the sections 0-2 cm. and 2-4 cm. from the tip, are the same. The acidic growth substances extractable from broad bean shoots are the same whether the plant material is boiled or frozen before extraction.