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.