What is the model that describes the movement of carbohydrates as a pressure-driven flow in plants?

The pressure-flow model, also known as the mass flow hypothesis, is the accepted explanation for how carbohydrates, particularly sucrose, are transported throughout a plant via the phloem. This model emphasizes the role of pressure differences that are generated in the phloem due to active loading of sucrose into the sieve tube elements. This loading process increases solute concentration, leading water to enter the phloem by osmosis, resulting in turgor pressure that drives the bulk movement of sap towards areas of lower pressure, such as sink tissues where carbohydrates are utilized or stored.

As a result, the movement of carbohydrates occurs through a pressure-driven flow that efficiently distributes nutrients throughout the plant, facilitating essential physiological functions. The elegance of this model lies in its ability to explain not only carbohydrate transport but also the rapidity of this process compared to passive transport mechanisms. Additionally, this model accounts for the bi-directional flow of nutrients, which is a crucial aspect of plant functioning.

In contrast, the capillary model primarily relates to the movement of water and solutes through small tubes and does not capture the dynamics of carbohydrate transport. The active transport model focuses on the energy-dependent transport of molecules across membranes rather than the pressure-driven flow of sap. The osmosis