ringing experiment

ringing experiment

a procedure in which the outer tissues of a stem are removed, leaving only the xylem and pith intact. Water transport up the stem is unimpeded by such a process, whereas food transport down from the leaves stops at the ring, thus demonstrating the roles of XYLEM and PHLOEM respectively
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005