Growth Substances in the Roots ofVicia faba

Abstract

An investigation has been made into the growth regulators present in ethanol extracts of the seedling roots of Vicia faba after separation on paper partition chromatograms, using segments of Avena coleoptiles and mesocotyls and of Pisum sativum.roots as biological assay material. Acetonitrile purification shows the presence of at least three auxins running in isobutanol: methanol: water, at Rfs of 0–0·25, 0·4–0·6, and 0·65–0·95; the latter may represent two different auxins. A similar, but clearer, picture is shown by the ether-soluble acid fraction. Here an auxin at Rf 0–0·25 also stimulates root growth and could be ‘accelerator α’. A second at Rf 0–0·25 is an indole compound which inhibits root growth and does not seem to be be IAA. A third at Rf 0·8–1·0 is also a root-growth inhibitor and gives no indole reaction. The ‘inhibitor β’ complex was demonstrated (Rf 0·65–0·85) together with a number of other inhibitors at lower Rf value. The ether-soluble neutral component also contains auxins or auxin precursors. The water-soluble, ether-insoluble fraction contains four readily interconvertible substances with auxin properties. They all appear to inhibit root growth and give no indole reaction.