Collection of phloem sap
Phloem saps were sampled applying centrifugation technique according to Hijaz and Killiny (2014). Briefly, the bark from young flush of M. domestica , P. communis and P. persica trees was manually removed with a clean scalpel and sliced into 2 cm pieces. After removing the bottom of a 0.5 ml Eppendorf tube, the tube was immersed in a second, larger tube (1.5 ml). Bark pieces were placed into the 0.5 ml tubes and centrifuged at 12,000 rpm at 4 °C for 10 min. The extracted phloem sap was collected and the refractive index, the density and the viscosity were determined.