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Experiments on the Transport of Auxin

1939; University of Chicago Press; Volume: 100; Issue: 3 Linguagem: Inglês

10.1086/334804

1940-1205

F. W. Went, R. G. White,

Flowering Plant Growth and Cultivation

1. Adapting the photokymograph recording of the Avena test, a new technique for measuring the velocity and capacity of the transport of growth promoting substances through different tissues has been worked out. For this the rate of bending and the moment of beginning of curvatures are compared for a normal Avena test and one in which the agar block is separated from the test plant through the tissue of which the transport properties are to be determined. Thus for individual pieces of tissue these properties can be calculated. 2. In general the results of van der Weij (6) were confirmed, as far as the transport properties of the Avena coleoptile are concerned. Transport velocity is independent of length of tissue, but the amount transported decreases with increased length of coleoptile section. Transport through the narrow or wide side of a coleoptile is practically the same. The lower part of the coleoptile has slightly different transport properties from the more apical zones. 3. The polarity of indoleacetic acid transport is far more pronounced than most of the earlier investigators found. In our experiments leakage along moist surfaces was more nearly excluded. Only the highest auxin concentrations (1000 mg./l.) were transported from base toward top through 3.1 and 4.2 mm. sections, but not through 6.3 mm. coleoptile sections. 4. There are great differences in transport velocity among various growth promoting substances. Owing to this and to differences in the rate of the growth reaction and limited transport capacity of the coleoptile cells, a wide variation results in the apparent growth activity of these substances in the Avena test. 5. Transport of indoleacetic acid through other plant tissues was determined, with positive results in corn coleoptile, papaya leaf stalks and midribs, Tropaeolum leaf stalks and flower stalks, and Nitella internodal cells.