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Transport of Thiamin in the Tomato Plant

James Bonner
American Journal of Botany
Vol. 29, No. 2 (Feb., 1942), pp. 136-142
Stable URL: http://www.jstor.org/stable/2437441
Page Count: 7
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Transport of Thiamin in the Tomato Plant
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Abstract

The distribution of thiamin in the tomato plant was investigated with the aid of an assay based on the thiamin requirement of Phycomyces Blakesleeanus. Data are presented to show that substances interfering with the assay are not present in tomato leaves. The highest concentration of thiamin in the vegetative plant was found in the youngest leaves. Each successively lower leaf contained a lower concentration of the substance. Thiamin accumulated markedly above a girdle made by steaming the stems of tomato plants at the second node. Thiamin accumulated markedly below a girdle made by steaming the stems of tomato plants in the region between the mature leaves and the young rapidly expanding leaves. The roots of decapitated plants from which all axillary shoots were removed contained more thiamin than the roots of decapitated plants from which axillary shoots were allowed to grow. Comparative thiamin accumulation in girdled petioles of leaves of different ages indicated that thiamin may be exported by mature leaves having relatively low concentrations of the material rather than by young leaves having higher concentrations of the substance.

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