Distribution of growth regulators and sugars by the tangential and radial transport systems of stem segments of Willow

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Abstract
The tangential transport of labelled growth regulators and sugars, through the bark of isolated stem segments of Willow (Salix viminalis L.), has been studied. It has been shown that these compounds have distinct patterns of distribution, particularly in the case of plant growth regulators. IAA moves preferentially into the lower half of a horizontal stem, kinetin into the upper half when these substances are applied via a bark abrasion made on the side of the stem. Distribution patterns of sugars were more variable, in some instances upward movement occurred, in others downward. The distinctness of the distribution patterns was accentuated by pretreatment of the stem segments in a horizontal position for 7 days prior to experimentation. Radial movement of labelled IAA and kinetin, centrifugally from the centre of the xylem to the bark, showed no difference in distribution between the upper and lower portions of the stem.