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Questions and Answers
What causes water to move into the plant cell osmotically?
What causes water to move into the plant cell osmotically?
- Higher osmotic potential of the solution compared to the cell
- Higher solute concentration in the cytosol than in the solution (correct)
- Higher pressure in the cytosol compared to the solution
- Lower solute concentration in the cytosol than in the solution
What is a consequence of ΨSsoln being greater than ΨScell?
What is a consequence of ΨSsoln being greater than ΨScell?
- Water leaves the cell
- The cell becomes plasmolyzed
- Water enters the cell
- The pressure potential of the cell increases (correct)
Which of the following is not a factor contributing to the turgor pressure of a plant cell?
Which of the following is not a factor contributing to the turgor pressure of a plant cell?
- Presence of a rigid cell wall
- Presence of a selectively permeable plasma membrane
- Presence of high atmospheric pressure (correct)
- High solute concentration in the cytosol
What condition results in no net water movement in a plant cell?
What condition results in no net water movement in a plant cell?
Which statement about turgor pressure is true?
Which statement about turgor pressure is true?
Which of the following states the relationship between ΨScell and ΨSsoln correctly?
Which of the following states the relationship between ΨScell and ΨSsoln correctly?
What happens to a plant cell when its ΨPcell is less than ΨPsoln?
What happens to a plant cell when its ΨPcell is less than ΨPsoln?
When a plant cell reaches equilibrium with its surrounding solution, what is true about its water potential?
When a plant cell reaches equilibrium with its surrounding solution, what is true about its water potential?
What role does the extensibility of the cell wall play in a less idealized cell?
What role does the extensibility of the cell wall play in a less idealized cell?
What effect does placing a less idealized cell in a solution with lower solute concentration than its cytosol have on the cell?
What effect does placing a less idealized cell in a solution with lower solute concentration than its cytosol have on the cell?
What condition leads to plasmolysis in a less idealized cell?
What condition leads to plasmolysis in a less idealized cell?
When a less idealized cell's solute potential (ΨS) is greater than that outside the cell, what happens?
When a less idealized cell's solute potential (ΨS) is greater than that outside the cell, what happens?
What is the primary characteristic of a plasma membrane (PM) in a less idealized cell?
What is the primary characteristic of a plasma membrane (PM) in a less idealized cell?
How does the selective permeability of the less idealized cell's PM affect water movement?
How does the selective permeability of the less idealized cell's PM affect water movement?
What occurs when the cell's turgor pressure (ΨPcell) increases?
What occurs when the cell's turgor pressure (ΨPcell) increases?
What happens to the cellular solute content when a less idealized cell is placed in a hypertonic solution?
What happens to the cellular solute content when a less idealized cell is placed in a hypertonic solution?
What happens to a plant cell when it is placed in a solution with higher osmotic strength?
What happens to a plant cell when it is placed in a solution with higher osmotic strength?
What is the turgor pressure of a flaccid cell?
What is the turgor pressure of a flaccid cell?
How does adding mannitol to a beaker of pure water affect osmotic potential?
How does adding mannitol to a beaker of pure water affect osmotic potential?
What is the relationship between solute potential (ΨS) and pressure potential (ΨP) in plasmolysis?
What is the relationship between solute potential (ΨS) and pressure potential (ΨP) in plasmolysis?
What happens to the concentration of solutes in the cell during plasmolysis?
What happens to the concentration of solutes in the cell during plasmolysis?
Which of the following statements correctly describes turgid cells?
Which of the following statements correctly describes turgid cells?
What could be inferred about a solution with a lot of mannitol added to it?
What could be inferred about a solution with a lot of mannitol added to it?
What does ΨP represent in the context of plant cells?
What does ΨP represent in the context of plant cells?
What does ΨP represent in the equation Ψ = ΨS + ΨP + ΨM?
What does ΨP represent in the equation Ψ = ΨS + ΨP + ΨM?
How does increasing pressure affect ΨP?
How does increasing pressure affect ΨP?
At standard atmospheric pressure, what is the value of ΨP?
At standard atmospheric pressure, what is the value of ΨP?
What happens to water movement in response to pressure gradients?
What happens to water movement in response to pressure gradients?
Which of the following statements about ΨP and atmospheric pressure is true?
Which of the following statements about ΨP and atmospheric pressure is true?
In plant tissues, what maximum value can ΨP reach?
In plant tissues, what maximum value can ΨP reach?
When atmospheric pressure is below standard atmospheric pressure, what happens to ΨP?
When atmospheric pressure is below standard atmospheric pressure, what happens to ΨP?
What is generally assumed regarding atmospheric pressure when calculating plant water relations?
What is generally assumed regarding atmospheric pressure when calculating plant water relations?
What happens to the protoplasm during plasmolysis?
What happens to the protoplasm during plasmolysis?
What is the relationship between ΨPcell and ΨSenvironment in a plasmolyzed cell?
What is the relationship between ΨPcell and ΨSenvironment in a plasmolyzed cell?
What effect does a concentrated solution have on onion epidermal cells?
What effect does a concentrated solution have on onion epidermal cells?
During plasmolysis, what remains attached to the cell wall?
During plasmolysis, what remains attached to the cell wall?
Which component largely composes the protoplasm in onion cells?
Which component largely composes the protoplasm in onion cells?
What does ΨP represent in the context of plasmolysis?
What does ΨP represent in the context of plasmolysis?
What is the typical observation when onion epidermal cells undergo turgor pressure?
What is the typical observation when onion epidermal cells undergo turgor pressure?
What is the role of anthocyanins in the vacuoles of onion cells?
What is the role of anthocyanins in the vacuoles of onion cells?
Study Notes
Water Potential Components
- Water potential (Ψ) is the sum of pressure potential (ΨP), solute potential (ΨS), and matric potential (ΨM): Ψ = ΨS + ΨP + ΨM.
- Pressure potential (ΨP) is the effect of pressure on water potential and is not affected by solute concentration. Increasing pressure increases the free energy of the system.
- Water moves from areas of higher pressure potential to lower pressure potential across a selectively permeable membrane.
- Standard atmospheric pressure (SAP) defines ΨP = 0 MPa (1 atm = 0.1013 MPa). ΨP > 0 MPa if atmospheric pressure (AP) exceeds SAP; ΨP < 0 MPa if AP is below SAP. Generally, ΨP = AP – SAP.
- In plant water relations calculations, slight deviations from SAP are often ignored, assuming AP = SAP = 0.1013 MPa. Plant tissues can have ΨP values up to 3 MPa.
Plant Cell Turgor
- Plant cell turgor results from a higher solute concentration in the cytosol compared to the outside, a selectively permeable plasma membrane (PM), and a cell wall preventing rupture.
- A high cellular solute concentration and cell wall lead to positive pressure potential (ΨPcell > 0).
Less Idealized Plant Cell
- A less idealized plant cell has a somewhat extensible cell wall, allowing volume changes.
- If placed in a solution with lower solute concentration than the cytosol, water moves into the cell osmotically, diluting the cellular solute content and increasing ΨPcell.
- If placed in a solution with higher solute concentration, water moves out osmotically, concentrating the cellular solute content and decreasing ΨPcell.
Plasmolysis
- Plasmolysis occurs when ΨScell > ΨS of the surrounding solution (i.e., solute concentration in the cell is lower than in the environment).
- During plasmolysis, the PM pulls away from the cell wall, and the protoplasm shrinks. ΨPcell becomes 0 MPa, and ΨScell equals the solute potential of the environment.
Red Onion Epidermal Peels and Plasmolysis
- Red onion epidermal peels are useful for visualizing plasmolysis due to the presence of anthocyanins (red pigments).
- In dilute solutions, cells are turgid (ΨP > 0 MPa). In concentrated solutions, protoplasm shrinks and pulls away from the cell wall, showing loss of turgor (ΨP = 0 MPa).
Turgid vs. Flaccid Cells
- A turgid leaf cell has a positive pressure potential (e.g., ~0.5 MPa), while a flaccid cell has zero turgor (ΨPcell = 0 MPa).
- Cells in plasmolysis have the same ΨP (0 MPa) but different ΨS, with plasmolyzed cells having a lower (more negative) ΨS.
Thought Experiment: Mannitol Addition
- Initially, in a beaker of pure water, Ψ = 0, ΨS = 0, and ΨP = 0.
- After adding mannitol, ΨS becomes negative, and ΨP remains unchanged (0 MPa) in an open container, meaning the overall water potential (Ψ) also becomes negative.
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Description
This quiz covers the key components of water potential, including pressure potential, solute potential, and matric potential. Understand how these factors influence water movement in plant cells and their significance in plant turgor. Test your knowledge on the equations and principles governing these concepts.
