Plants - Translocation.

Translocation is the movement of dissolved substances or assimilates through the plant. It requires energy and occurs in the Phloem. It moves from the Source: where it is made, a high concentration to the Sink: where it is used up, a low concentration. Enzyme maintain the concentration gradient from the source by breaking down the solutes at the sink.

The Mass Flow Hypothesis:

Scientists are really sure how translocation occurs but the mass flow hypothesis is the most supported.

At the Source:

Sugars are loaded into the Phloem by Companion cells, the water potential decreases, the water moves down, hydrostatic pressure increases the sugars flow to the Sink.

At the Sink:

Solutes are stored by enzymes inside the storage cells. This increases the water potential meaning that the water also leaves.  

Companion Cells (at the Source):

These contain large numbers of mitochondria making the 'A' 'T' 'P' needed for the active transport part of…