A continuous high osmotic concentration is maintained in region P, which loads a sieve tube element by passively transporting solute molecules into it.

R shows the movement of H₂O into sieve tube elements from nearby xylem vessels by osmosis.

Translocation of organic solutes takes place from region P with high turgor pressure to region Q with low turgor pressure.

In region Q, material is either consumed or is converted into insoluble storage forms resulting in decreased osmotic pressure.