Translocation moves sugar from a source to a sink via phloem.

  1. Loading of sugar into the sieve tube at the source reduces water potential inside the sieve-tube. This causes the tube to take up water by osmosis.

  2. Uptake of water generates positive pressure that forces the sap to flow along the tube.

  3. The pressure is relieved by the unloading of sugar and water from the tube at the sink.

  4. Xylem recycles water from sink to source.
Translocation in summer:

Translocation in spring: