Effects of Rootstocks and Interstocks on the Xylem Sap Composition in Apple Trees: Effects on Nitrogen, Phosphorus, and Potassium Content

This paper records the concentration of N, P, and K in sap whichexuded from the cut stumps of composite orchard apple trees.The trees were either single-worked on different rootstocksor incorporated various interstocks. While the volume of sap exuded per unit area of cut surfacedid not appear to vary with rootstock or interstock, exudatefrom the dwarfing rootstocks or interstocks contained depletedlevels of nutrients. A possible mechanism for rootstock and interstock effects isdiscussed in the light of these results.