Pressure-flow hypothesis

    Sugar produced during photosynthesis in the leaves is transported throughout the plant via the phloem. In the leaves, sucrose is actively loaded into the phloem sieve tubes, which increases the osmotic pressure inside these tubes. Water then enters by osmosis, creating a high pressure environment that drives the sugar-rich solution to areas of lower pressure, known as sinks, such as roots. This process, known as pressure-flow hypothesis, ensures that sugars are efficiently distributed to support various functions like growth, storage, and reproduction.

    The difficulty in proving the pressure-flow hypothesis arises primarily from technical challenges. The phloem channels that transport sugars are extremely delicate and hard to access without disrupting their function, making direct measurements nearly impossible. Additionally, the dynamic changes in pressure and flow within the phloem occur in a living, complex system, which current imaging sensor technologies cannot monitor accurately in real time. This combination of physical inaccessibility and technological limitations means that we rely on indirect evidence and modeling rather than direct, conclusive proof.

Microsoft Copilot and Edited

phloem: DJ[ˋfləuem]