Translocation of the Floral Stimulus in Xanthium

Abstract

Studies were made of the translocation of the floral stimulus in X. pennsylvanicum by means of inarch graft arrangements made through lens paper and rice paper impregnated with lanolin or other materials, by direct stem contact, by the killing of petiole sections and by the removal of stem tissues. The floral stimulus crossed an inarch contact between an induced donor plant and a receptor plant only when tissue union was established and direct tissue contact was uninterrupted for 4 days. . It failed to be translocated downward from an induced leaf through dead petiole tissue or through functional xylem cells. The floral stimulus also failed to be translocated from an induced donor branch of a 2-branched plant to a receptor branch when the bark was removed from the donor branch below the induced leaves or from the receptor branch immediately above the point of branching. The floral stimulus appeared to be translocated both up and down the stem chiefly in the bark.