The interchange of 14C-kinetin and 14C-gibberellic acid between the bark and xylem of willow

Abstract
Considerable two-way interchange of label derived from 14C-GA3 and 14C-kinetin has been shown to occur between the xylem and extra-cambial tissue of Salix viminalis L. Radial translocation of both growth substances from the transpiration stream to the sieve-tube sap has been demonstrated by the use of an aphid technique. This is the first record of the bark-xylem interchange of these two growth hormones. A high percentage of 14C-label is present in compounds other than GA3 and kinetin 8 hours after application. Mechanisms of lateral transfer are discussed together with their possible physiological significance.