Question

Explain the mass flow hypothesis of transport in phloem.

Answer 1

In 1930, Munch proposed the mass flow hypothesis which explains the movement of sap through the phloem. When there is a high concentration of sugar present in the source (which is where the food is prepared) then a diffusion gradient gets created between the sugar source and the sugar shrink where the sugar is stored. This is responsible for drawing water into the cells from the neighbouring xylem. When this happens, turgor pressure gets created (bidirectional movement).