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

Considerable two-way interchange of label derived from (14)C-GA3 and (14)C-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 (14)C-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.