Phloem – Transportation of Minerals (i.e sugars)
A high concentration of organic substance inside cells of the phloem at a source, such as a leaf, creates a diffusion gradient (osmotic gradient) that draws water into the cells. Movement occurs by bulk flow (mass flow); phloem sap moves from sugar sources to sugar sinks by means of turgor pressure, also known as hydrostatic pressure. A sugar source is any part of the plant that is producing or releasing sugar. During the plants growth period, usually during the spring, storage organs such as the roots are sugar sources, and the plants many growing areas are sugar sinks.
sink – where sugar is transported to and then off loaded to where
there is a collection of sugar after photosynthesis
source – where materials are loaded into from phloem
b/c the phloem will be hypertonic to its surrounding, water goes into the phloem and the increase in pressure makes the water and sugar move up the platn.