Some Constituents of Xylem Sap and their Possible Relationship to Xylem Differentiation

Bleeding sap of Actinidia chinensis and Betula populifolia and guttation fluidof Avena sativa were analysed for sugars, amino-acids, auxin, and certain enzymes. A wide range of amino-acids was found in all three. Auxin was not detected in the bleeding sap, but was present in Avena guttation fluid (5.1 μg IAA equivalent/l). ‘IAA oxidase’, acid phosphatase, ribonuclease, deoxyribonuclease, and protease were detected in the bleeding sap and guttation fluid. The possibility that some of the substances found in sap and guttation fluid are products of autolysing, differentiating xylem cells in the roots is discussed.