How does sap move from the sieve tube into a sink?

Question

Quizplus · Accepted Answer

Sap moves from the sieve tube into a sink by pressure flow or mass flow. The source cells, where the sugar is produced by photosynthesis, have a higher pressure potential than the sink cells, where the sugar is needed for energy or storage. This creates a pressure gradient that drives the flow of sap from the source to the sink. As a result, the sap moves from an area of high pressure to an area of low pressure without the need for a pump or active transport.

How Does Sap Move from the Sieve Tube into a Sink