The Pressure Flow Hypothesis, also known as the Mass Flow Hypothesis, is the best-supported theory to explain the movement of sap through the phloem. It was proposed by Ernst Munch, a German plant physiologist in 1930.
Pressure Flow Hypothesis. Now that we've covered sinks and sources, let's look at the pressure flow hypothesis. This model of how phloem works is based on the relationship between sinks and sources.
Mass-flow hypotheses include the pressure-flow hypothesis, which states that flow into sieve tubes at source regions (places of photosynthesis or mobilization and exportation of storage products) raises the osmotic pressure in the sieve tube; removal of sugars from sieve tubes in sink regions—i.e ...
A model, called the pressure flow model, describes how sucrose concentrations determine the direction of the flow. 4. Two types of cells—source cells and sink cells—play roles in the transport ...
Munch Pressure Flow Model. Munch, a German plant physiologist, proposed in 1930, a simple physical model which can be tested in the laboratory for the mechanism of phloem transport. As shown in Figure, two osmometers, one containing solute at higher concentration .(A) than the other (B), are connected by a tube (C) and dipped in water.
In very general terms, the pressure flow model works like this: a high concentration of sugar at the source creates a low solute potential (Ψs), which draws water into the phloem from the adjacent xylem. This creates a high pressure potential (Ψp), or high turgor pressure, in the phloem.
Biology: Pressure flow hypothesis. STUDY. PLAY. Terms in this set (...) pressure-flow hypothesis. a hypothesis that states that sugars are actively transported into sieve tubes through osmosis where pressure builds at the source and reduces at the sink causing the flow from source to sink.
This video explains the pressure flow hypothesis, an explanation for how sugars are transported through the vascular tissue of a plant.
Best Answer: The pressure flow model is used to explain movement of materials in phloem. Sugar is actively transported and water follows by osmosis. The resulting pressure difference moves the fluid from a source (site of sugar production) to a sink (site of sugar use).
The Pressure-Flow Model. STUDY. PLAY. Step 1. Sugar from a source enters the phloem by active transport. Step 2. When the sugar concentration in the phloem increases, water enters the sieve tubes in phloem from xylem by osmosis. Step 3. Pressure builds up inside the sieve tube cells and pushes sugar through the sieve tubes. The sugar moves at a ...