What does the pressure-flow model explain?

The pressure-flow model explains how sugars and other organic nutrients are transported in plants through the phloem. According to this model, differences in turgor pressure between source (where sugars are produced) and sink (where they are used or stored) tissues drive the flow of the sap. As sugars are actively loaded into the phloem at the source, water follows osmotically, increasing pressure and pushing the sap toward the sink, where sugars are unloaded and water is recycled. This process allows for efficient distribution of energy resources throughout the plant.