What is mass flow theory a level biology?
The mass flow hypothesis is a theory which attempts to explain how solutes are transported from source cells into sinks through the phloem.
What does the term mass flow mean?
mass transferMass flow, also known as “mass transfer” and “bulk flow”, is the movement of fluids down a pressure or temperature gradient, particularly in the life sciences. As such, mass flow is a subject of study in both fluid dynamics and biology.
Who describe the mass flow hypothesis?
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 Münch, a German plant physiologist in 1930.
What is mass flow in ecology?
oxford. views 1,428,169 updated May 29 2018. mass flow (pressure flow) A hypothesis to explain the movement of sugars in the phloem tissue of plants. At a source (site of production) sugars are actively secreted from phloem companion cells into the sieve elements, causing water to follow by osmosis.
How is mass flow different from diffusion?
The key difference between bulk flow and diffusion is that bulk flow is the movement of a fluid or a mass due to a pressure gradient while diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration along the concentration gradient.Nov 2, 2020
What is mass flow rate divided by volumetric flow?
The mass flow rate is related to the volumetric flow rate as shown in Equation 3-2 where r is the density of the fluid. If the volumetric flow rate is in cubic feet per second and the density is in pounds-mass per cubic foot, Equation 3-2 results in mass flow rate measured in pounds-mass per second.
What is Munch theory?
Abstract. In the 1920s, the German forestry scientist Ernst Münch postulated that photo-assimilate transport is a mass flow driven by osmotically induced pressure gradients between source organs (high turgor) and sink organs (lower turgor).
Does mass flow require energy?
The actual pathway of nutrients into the root itself may be passive (no energy required; the nutrient enters with water) or active (energy required; the nutrient is moved into the root by a "carrier" molecule or ion)....NutrientIronMass FlowXDiffusionXRoot InterceptionX11 more columns
What is the girdling experiment?
The experiment involves the removal of all the tissue outside to vascular cambium (bark, cortex, and phloem) in woody stems except xylem. The experiment involves the removal of all the tissue outside to vascular cambium (bark, cortex, and phloem) in woody stems except xylem.May 5, 2018
What is pressure flow theory?
The Pressure-Flow Hypothesis Figure 16.2.2.3 Pressure flow. The best-supported theory to explain the movement of food through the phloem is called the pressure-flow hypothesis. It proposes that water containing food molecules flows under pressure through the phloem.Dec 31, 2020
How mass flow occurs in plants?
A highly concentrated organic sugar especially sugar in the cells of phloem from a source like a leaf forms a diffusion gradient which draws water in the cells from adjacent xylem. This develops turgor pressure in the phloem which is also called as hydrostatic pressure.Aug 15, 2020
Does mass flow occur in xylem?
Mass transport in plants takes place in the xylem, which carries water and inorganic ions, and phloem, which carries sugars and amino acids. Water in the xylem moves in one direction and is driven by the transpiration stream.
What is the mass flow hypothesis?
The mass flow hypothesis states that the translocation of glucose and other sugars within the phloem is caused by a never-ending flow of water and dissolved nutrients between the source (a place where sugars are made) and sink (where sugars are utilized). A diffusion gradient or osmotic gradient is caused by the phloem source cells due to ...
Which theory proposes that not every plant utilizes the phloem for active transportation?
The most popular theory proposed besides the mass flow hypothesis in plants is Robert Turgeon's polymer trap mechanism theory.
How does water travel from the xylem to the source cells?
At the same time, water travels from nearby xylem to the source cells via osmosis to increase hydrostatic pressure in the elements of the sieve tube. This is the mass flow hypothesis for the mechanism of translocation in plants. This hydrostatic pressure turgor then shifts the sugars and other substances down the cells of the sieve tube towards ...
What causes a diffusion gradient?
A diffusion gradient or osmotic gradient is caused by the phloem source cells due to the high concentration of sugar and other organic substances. This results in water being drawn out from adjacent xylem and hydrostatic pressure which moves the sap. This theory is the closest explanation available to describe mass flow in phloem.
How does the creation of food affect the osmotic pressure of a sieve tube?
The creation of food raises osmotic pressure within the sieve tube. This removes the sugars from sieve tubes towards the sink regions (the place where utilization of materials takes place) to lower the pressure. A potential is created from the source to the sink within the sieve tubes, in which the solution flows.
What is the process of moving minerals and water through the xylem?
Translocation is the movement of minerals and water through the xylem as a result of negative pressure and movement through the phloem as the result of hydrostatic pressure. This movement is accompanied by the process of phloem loading and unloading.
How do cells present in food sources load a sieve tube through osmotic potentials, pushing the
The cells present in food sources load a sieve tube through osmotic potentials, pushing the sap lower. These cells then deliver the solutes out of the sieve-tube producing the unloading effect. When asked to explain mass flow hypothesis in details, this is the answer:
What is Mass Flow Hypothesis?
Mass flow hypothesis or pressure-flow hypothesis is a theory that originated in 1930. It was a German plant physiologist, named Ernst Munch, who worked upon it to explain the concept of movement or transportation of sap through phloem in a plant.
Mass Flow Hypothesis Mechanism
The mechanism of mass flow is driven by multiple concepts. Let us have a look at some of them:
Criticism of Mass Flow Hypothesis
There is a lot of criticism related to mass flow hypothesis theory. Some of them are:
Things to Remember
Mass flow hypothesis involves great experiments and facts and was propounded by Ernst Munch.
Sample Questions
Ans. Mass flow hypothesis or pressure-flow hypothesis is a theory that originated in 1930. It was a German plant physiologist, named Ernst Munch, who worked upon it to explain the concept of movement of sap through phloem in a plant.
What is mass flow?
Mass flow, also known as “mass transfer” and “bulk flow”, is the movement of fluids down a pressure or temperature gradient, particularly in the life sciences. As such, mass flow is a subject of study in both fluid dynamics and biology. Examples of mass flow include blood circulation and transport of water in vascular plant tissues.
What are some examples of mass flow?
Examples of mass flow include blood circulation and transport of water in vascular plant tissues. Mass flow is not to be confused with diffusion which depends on concentration gradients within a medium rather than pressure gradients of the medium itself.
Why does the upward flow of xylem water stop?
If an air bubble forms, the upward flow of xylem water will stop because the pressure difference in the vessel cannot be transmitted.
How is solute flow driven?
Solute flow is driven by a difference in hydraulic pressure created from the unloading of solutes in the sink tissues. That is, as solutes are off-loaded into sink cells (by active or passive transport), the density of the phloem liquid decreases locally, creating a pressure gradient.
What is bulk flow in plant biology?
Plant biology. In general, bulk flow in plant biology typically refers to the movement of water from the soil up through the plant to the leaf tissue through xylem, but can also be applied to the transport of larger solutes (e.g. sucrose) through the phloem .
How does water transport in xylems work?
According to cohesion-tension theory, water transport in xylem relies upon the cohesion of water molecules to each other and adhesion to the vessel's wall via hydrogen bonding combined with the high water pressure of the plant's substrate and low pressure of the extreme tissues (usually leave s).
Learn about this topic in these articles
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., those in…
explanation for phloem transport
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., those in…
Mechanism- How It Works
- Translocation is the movement of minerals and water through the xylem as a result of negative pressure and movement through the phloem as the result of hydrostatic pressure. This movement is accompanied by the process of phloem loading and unloading.
So How Can You Describe The Mass Flow Hypothesis?
- The cells present in food sources load a sieve tube through osmotic potentials, pushing the sap lower. These cells then deliver the solutes out of the sieve-tube producing the unloading effect. When asked to explain mass flow hypothesis in details, this is the answer: 1. Plants respire through the process of photosynthesis, which involves the formation of glucose in mesophyll cel…
Criticisms of The Mass Flow Hypothesis
- The majority of people rejecting this hypothesis believe that mechanisms such as the mechanism of translocation in plants take place due to metabolic processes, not hydrostatic pressure. Critics believe that mass flow is mainly a passive process and companion cells support sieve tube vessels. This indicates that the hypothesis negates phloem's livi...
Fun Fact
- The mass flow hypothesis mechanism was sourced from Ernst Munch’s book Die Stoffbewegungen in der Pflanze (translated to The Movements of Matter in Plants), with 230 pages dedicated to just fluid circulation within plants. Interestingly, Munch claimed that his concept was nothing novel; his famed colleagues had understood it before he did. No other bota…
What Is Mass Flow Hypothesis?
- Mass flow hypothesis or pressure-flow hypothesis is a theory that originated in 1930. It was a German plant physiologist, named Ernst Munch, who worked upon it to explain the concept of movement or transportationof sap through phloem in a plant. This hypothesis explains that the presence of highly concentrated and organic sugar in the cell of phloe...
Mass Flow Hypothesis Mechanism
- The mechanism of mass flow is driven by multiple concepts. Let us have a look at some of them: 1. Beginning with process of translocation, which states about the negative pressure which is mainly responsible for movement of minerals and water via xylem and hydrostatic pressure which is, on the other hand, responsible for the movement via phloem. 2. This process of translocatio…
Criticism of Mass Flow Hypothesis
- There is a lot of criticism related to mass flow hypothesis theory. Some of them are: 1. Many critics believed that process of translocation happens due to metabolic process and not due to hydrostatic pressure. 2. As the hypothesis talks about the uniform rate of transmission of material inside phloem and sieve tube, critics have disagreed with the same. 3. Critics also argued that th…
Things to Remember
- Mass flow hypothesis involves great experiments and facts and was propounded by Ernst Munch.
- This great theory was manifested in his book where he simply dedicated 230 pages only to the fluid circulation within plants.
- However, even after propounding something so novel, Munch never realized that it was origin…
- Mass flow hypothesis involves great experiments and facts and was propounded by Ernst Munch.
- This great theory was manifested in his book where he simply dedicated 230 pages only to the fluid circulation within plants.
- However, even after propounding something so novel, Munch never realized that it was original and new.
- As per mass flow hypothesis, Sucrose has the tendency of getting diffused into sieve tube from neighbor cells.
