The Auxin Activity Extractable from Excised Tomato Roots by Cold 80 per cent. Methanol

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Abstract
Extracts of excised tomato roots prepared with cold aqueous methanol have been partitioned between ethyl acetate and water and chromatograms of the two fractions bioassayed by an Avena coleoptile straight growth test and sprayed with various reagents including those giving colour reactions with indole compounds. The greater part of the auxin activity is in the aqueous fraction and chromatograms of this fraction give positive indole reactions. The aqueous fraction chromatographed with isopropanol/ammonia/water shows two zones of growth-promoting activity. The zone of lower Rf contains tryptophane and unidentified ninhydrin-positive material. Tryptophane accounts for the activity of the Ehrlich-positive region of this zone. The activity of the zone of higher Rf is associated with ninhydrin-positive material; this activity can, by use of other solvents, be distinguished in Rf from that of the common amino-acids which would occur in this zone on the primary chromatograms. Chromatograms of the aqueous fraction also show the presence of urea and of a phenol, neither of which are associated with the zones of growth-promoting activity. The ethyl acetate fraction, and particularly the acid fraction of this, contains growth-promoting activity which, in a range of solvents, always corresponds in Rf to IAA. The acid fraction contains a growth inhibitor corresponding in Rf to the β-inhibitor of other workers. A zone of growth-promoting activity near the solvent front on isopropanol/ammonia/water chromatograms contains more than one active component, but IAN appears to be absent.

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