Question

In the pressure flow hypothesis, what would be the osmotic pressure at the sink?

Answer 1

Hint:
The pressure flow hypothesis is the best-supported hypothesis to describe the movement of sap via the phloem. A high concentration of organic matter, especially sugar, in phloem cells from a source such as leaves creates a diffusion gradient (osmotic gradient) that draws water from the adjacent xylem into the cells. This forms turgor pressure, also called hydrostatic pressure, in the phloem. The movement of phloem sap occurs as mass flow from sugar sources to sugar sinks. Movement in the phloem is bidirectional, while in xylem cells it is unidirectional (upward).

Complete step by step answer:
The pressure flow hypothesis is the best-supported hypothesis to describe the movement of sap via the phloem. A high concentration of organic matter, especially sugar, in phloem cells from a source such as leaves creates a diffusion gradient (osmotic gradient) that draws water from the adjacent xylem into the cells. This forms turgor pressure, also called hydrostatic pressure, in the phloem. The movement of phloem sap occurs as mass flow from sugar sources to sugar sinks. Movement in the phloem is bidirectional, while in xylem cells it is unidirectional (upward).

Note:
Because of the multidirectional flow and the fact that sap cannot easily move between adjacent sieve tubes, it is not unusual for sap from neighbouring sieve tubes to flow in opposite directions.