Answer:
Sugar is stored in the sink.
Cells use this sugar for cellular respiration. Water exits by osmosis and returns to the xylem.
Explanation:
Pressure flow hypothesis is known as the theory to define the motion of sap with the help of phloem. A high concentration of substances such as sugar, inside cells of the phloem which is present in the leaves creates an osmotic gradient which helps to draw water into the cells from the xylem.
This creates hydrostatic pressure in the phloem. By bulk flow motion of phloem sap occurs from sugar sources to sugar sinks. In phloem this movement is bidirectional, and in xylem this movement is unidirectional.
