Translocation in Plants Possessing Supernumerary Phloem

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Abstract
The translocation path in the included phloem of Bougainvillea and in the bicolateral bundles of cucumber was studied by exposing young branches to 14CO2 and detecting the radioactive compounds by autoradiography. In Bougainvillea, the structure and function of the phloem system is comparatively uncomplicated and uniform. All phloem bundles, i. e. those which are located in parenchymatous tissue of the central zone and those embedded in the secondary xylem, become labelled. Exogenous IAA was translocated in the bundles, but the exact mode of translocation was not ascertained. Apical dominance was not affected by girdling. The implication of this fact is discussed with respect to the translocation of the auxin that determines the correlative inhibition involved in apical dominance. In cucumber the inner phloem became labelled throughout the plant to a lesser extent than the outer phloem. However, in the petiole of the assimilating leaf the intensity of the label was the same in both inner and outer phloem, although the inner phloem has fewer elements. Below the treated leaf the inner phloem translocated less than the outer phloem. Above this leaf the inner phloem was entirely unlabelled

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