Auxins and Auxin Precursors in Acid and Nonacidic Fractions of Plant Extracts. Contributions from the Hull Botanical Laboratory 641

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Abstract
Etiolated pea-stem internodes extracted with ether at 22[degree]C. showed an increase in rate of production of nonacidic growth substance between the 1st and 4th hours of extraction over the rate during the 1st hour, while the production rate of acid growth substance fell during the same period, as measured with the Avena coleoptile curvature test. The rate of production of acid growth substance at 0''C. was about half that at 22[degree]C. during the 1st hour, and after the 1st hour of extraction the rate fell and remained low at both 0 s and 22[degree]C. No nonacidic growth substance could be extracted from the internodes at 0''C. during 24 hours. The presence of a nonacidic auxin precursor was indicated in nonacidic fractions of ether extracts of pea internodes and in nonacidic fractions of juice of such tissue and of etiolated cabbage leaves. This precursor could be converted into active auxin by Avena coleoptile juice. The presence of an acid auxin precursor was indicated in acid ether fractions of the juice of the pea tissue and of etiolated cabbage leaves, and this precursor could be converted similarly.