Quick Review Flashcards - Click to flip and test your knowledge!
Question
What are the two primary functions of plant roots?
Answer
Roots fix the plant in the soil and absorb water and mineral nutrients.
Question
Which four processes inside the plant body require water?
Answer
Water is needed for photosynthesis, transpiration, transportation, and mechanical stiffness.
Question
What is the role of water in the process of photosynthesis?
Answer
Water serves as a raw material for the synthesis of glucose.
Question
How does transpiration benefit a plant during hot weather?
Answer
It provides cooling through the evaporation of water vapour.
Question
Which condition of plant cells provides mechanical stiffness to tissues?
Answer
Turgidity, or being fully distended with water, provides stiffness.
Question
In what form are mineral nutrients typically absorbed from the soil?
Answer
They are absorbed as salts or as simple ions such as $K^{+}$, $Ca^{2+}$, and $Mg^{2+}$.
Question
Which three characteristics of roots enable them to draw water efficiently from the soil?
Answer
Roots have an enormous surface area, high cell sap concentration, and thin-walled root hairs.
Question
How does the surface area of root hairs compare to the length of the main root?
Answer
The total length and surface area of root hairs are enormous, often covering many kilometres.
Question
Why is the high concentration of cell sap in root hairs significant for water absorption?
Answer
It creates the necessary concentration gradient for osmosis to occur from the soil.
Question
Describe the permeability of a root hair's cell wall.
Answer
The cell wall is thin and completely permeable to water and dissolved substances.
Question
Describe the permeability of a root hair's cell membrane.
Answer
The cell membrane is very thin and semi-permeable.
Question
What defines the process of imbibition?
Answer
Imbibition is the absorption of water by living or dead plant cells through surface attraction.
Question
Which plant substances have a strong affinity for water during imbibition?
Answer
Cellulose and proteins are hydrophilic substances that imbibe water.
Question
What is the definition of diffusion in a biological context?
Answer
Diffusion is the free movement of molecules from a region of higher concentration to lower concentration when in direct contact.
Question
What is the definition of osmosis?
Answer
Osmosis is the movement of water molecules from a region of higher concentration to lower concentration through a semi-permeable membrane.
Question
In osmosis, water moves from a _____ solution to a _____ solution.
Answer
dilute; concentrated
Question
What is endosmosis?
Answer
Endosmosis is the inward diffusion of water through a semi-permeable membrane when the surrounding solution is less concentrated.
Question
What is exosmosis?
Answer
Exosmosis is the outward diffusion of water through a semi-permeable membrane when the surrounding solution is more concentrated.
Question
A semi-permeable membrane allows the passage of _____ but prevents the passage of _____.
Answer
solvent molecules; solute molecules
Question
What determines the state of osmotic equilibrium between two solutions?
Answer
Equilibrium is reached when the concentration of water molecules becomes equal on both sides of the membrane.
Question
Define osmotic pressure.
Answer
Osmotic pressure is the minimum pressure required to prevent the passage of pure solvent into a solution through a semi-permeable membrane.
Question
What does the term 'tonicity' refer to in plant physiology?
Answer
Tonicity is the relative concentration of solutions that determines the direction and extent of diffusion.
Question
How is an isotonic solution defined?
Answer
An isotonic solution has a relative concentration of water and solute equal to that inside the cell.
Question
What happens to a cell placed in a hypotonic solution?
Answer
Water moves into the cell via endosmosis, causing the cell to swell.
Question
What happens to a cell placed in a hypertonic solution?
Answer
Water moves out of the cell via exosmosis, causing the cell to shrink.
Question
Why might a red blood cell burst in a hypotonic solution while a plant cell merely becomes turgid?
Answer
Plant cells have a rigid cell wall that resists bulging and prevents bursting.
Question
What is active transport?
Answer
Active transport is the passage of a substance from lower to higher concentration using energy from the cell in the form of $ATP$.
Question
How does the direction of active transport relate to the direction of diffusion?
Answer
Active transport occurs in a direction opposite to that of diffusion.
Question
Define the state of turgidity in a plant cell.
Answer
Turgidity is the state where a cell is rigid and stretched by an increase in vacuole volume due to water absorption.
Question
What is turgor pressure?
Answer
Turgor pressure is the pressure exerted by the cell contents against the cell wall.
Question
What is wall pressure?
Answer
Wall pressure is the pressure exerted by the cell wall against the cell contents.
Question
What is flaccidity in a plant cell?
Answer
Flaccidity is the condition where cell content is shrunken and the cell is no longer tight or distended.
Question
Define plasmolysis.
Answer
Plasmolysis is the contraction of cytoplasm from the cell wall caused by water withdrawal in a hypertonic solution.
Question
Define deplasmolysis.
Answer
Deplasmolysis is the recovery of a plasmolysed cell as it returns to a turgid state upon re-entry of water.
Question
How does turgidity assist the leaves of a plant?
Answer
It provides rigidity to soft tissues, keeping leaves spread out for photosynthesis.
Question
What causes the wilting of leaves in the hot afternoon sun?
Answer
Wilting occurs when water loss through transpiration exceeds water absorption through the roots.
Question
Why is salting meat an effective method for killing bacteria?
Answer
Salting causes plasmolysis, drawing water out of the bacterial cells and killing them.
Question
What determines the opening and closing of stomata?
Answer
The opening and closing are controlled by the turgidity of the guard cells.
Question
Explain the turgor movement in the sensitive plant ($Mimosa$ $pudica$).
Answer
Touching a leaf causes a loss of turgor at the base of the leaflets (pulvinus), making them droop.
Question
What is root pressure?
Answer
Root pressure is the upward pressure developed in roots due to continued inward cell-to-cell osmosis.
Question
What is guttation?
Answer
Guttation is the loss of excessive water as droplets from the margins or tips of leaves due to high root pressure.
Question
Which plant tissue is responsible for the upward conduction of water and minerals?
Answer
Xylem is the tissue responsible for upward conduction.
Question
Which plant tissue is responsible for the downward conduction of manufactured food?
Answer
Phloem is the tissue responsible for downward conduction.
Question
What are the four main forces contributing to the ascent of sap?
Answer
The forces are root pressure, capillarity, transpirational pull, and adhesion.
Question
How does capillarity contribute to the ascent of sap?
Answer
Narrow xylem vessels cause water to rise to fill the vacuum created by transpiration.
Question
Define transpirational pull.
Answer
Transpirational pull is the suction force created as water evaporates from leaves, pulling more water molecules upward.
Question
What is cohesion in the context of water movement in plants?
Answer
Cohesion is the molecular attraction that keeps water molecules joined in a continuous column.
Question
What is adhesion in the context of water movement in plants?
Answer
Adhesion is the force that causes water to stick to the surfaces of the xylem cells.
Question
What is the purpose of the 'ringing' or 'girdling' experiment?
Answer
It demonstrates that phloem conducts food downwards while xylem conducts water upwards.
Question
In a girdling experiment, why does the stem swell above the ring?
Answer
The sap containing manufactured food accumulates above the cut phloem.
Question
What does the term 'bleeding' refer to in plants?
Answer
Bleeding is the loss of cell sap through a cut or injured stem due to root pressure.
Question
Which specific instrument is used to demonstrate and measure root pressure?
Answer
A manometer is used to measure root pressure.
Question
Why is oil added to the top of water in root absorption experiments?
Answer
Oil is added to prevent the loss of water from the beaker by evaporation.
Question
The process by which wooden doors swell during the rainy season is _____.
Answer
imbibition
Question
What chemical stain is commonly used to show that water is conducted through xylem?
Answer
Eosin solution is used to stain the xylem vessels pink.