Question 1

When an animal cell is placed in a hypotonic solution and water enters the cell via osmosis, the volume of the cell increases until it bursts. Which of the following explains why this does not happen to plant cells?

Accepted Answer

Plant cells have cell walls that provide structural support and exert turgor pressure, which counteracts the osmotic pressure from incoming water, preventing the cell from bursting.

Question 2

Which of the following contribute to the surface area available for water absorption from the soil by a plant root system?
I. root hairs
II. endodermis
III. mycorrhizae
IV. branching

Accepted Answer

I. Root hairs increase the surface area directly by extending from the root into the soil. III. Mycorrhizae are symbiotic relationships between fungal hyphae and plant roots that effectively increase the surface area for water and nutrient absorption. IV. Branching of roots increases the overall surface area available for absorption by creating more points of entry for water and nutrients.

Question 3

Which of the following observations provides the strongest evidence against root pressure being the principal mechanism of water transport in the xylem?

Accepted Answer

Root pressure is not sufficient to move water over long distances in tall plants, indicating that other mechanisms, such as transpiration pull, play a more significant role in water transport through the xylem.

Question 4

The value for Ψ in root tissue was found to be -0.15 MPA. Which of the following best describes water flow if the root tissue was placed it in a 0.1 M solution of sucrose (Ψ = -0.23 MPa)?

Accepted Answer

Water potential is lower in the root tissue (-0.15 MPa) than in the sucrose solution (-0.23 MPa), so water will flow from the tissue into the sucrose solution to equalize the water potential.

Question 5

Which of the following are important components of long-distance transport process in xylem?
I. the cohesion of water molecules
II. a negative water potential
III. the active transport of solutes
IV. bulk flow from source to sink

Accepted Answer

I. The cohesion of water molecules is crucial for the movement of water through the xylem in plants, as it allows for the continuous column of water to be pulled up from the roots to the leaves. II. A negative water potential gradient is necessary for the movement of water from the soil into the plant roots and then upwards through the xylem. III. Active transport of solutes is more relevant to the phloem and the movement of nutrients, not the xylem. IV. Bulk flow from source to sink describes the movement of sugars in the phloem, not water in the xylem.

Question 6

Long-distance transport in phloem requires which of the following processes?
I. a positive water potential
II. active transport through parenchyma cells
III. cohesion between water molecules
IV. evaporation of water molecules

Accepted Answer

Long-distance transport in phloem involves a positive water potential to drive the flow of sap, active transport through parenchyma cells to load and unload sugars, and cohesion between water molecules to maintain the flow. Evaporation of water molecules is related to the xylem, not phloem.

Question 7

The graph below shows daily water potential in the xylem of a woody plant. Which of the following statements is best supported using the data?

Accepted Answer

The answer of The graph below shows daily water potential...

Question 8

How does the same cell differ if it is a flaccid cell compared to a turgid cell?

Accepted Answer

CA flaccid cell has lower pressure potential because it is not as full of water, leading to less pressure on the cell walls. It also has higher solute potential because there is a higher concentration of solutes inside the cell compared to its surroundings, which is a condition that leads to the cell being flaccid as it loses water to balance solute concentrations.

Question 9

If Ψ P = 0.3 MPa and ΨS = -0.45 MPa what will be the resulting Ψ?

Accepted Answer

The resulting water potential (Ψ) is the sum of the pressure potential (ΨP) and the solute potential (ΨS). Therefore, Ψ = ΨP + ΨS = 0.3 MPa + (-0.45 MPa) = -0.15 MPa.

Question 10

A water molecule could move all the way through a plant from soil to root to leaf to air and pass through a living cell only once. This living cell would be a part of which structure?

Accepted Answer

The endodermis is the only layer of cells in a plant through which water must pass to enter the vascular system from the soil. It acts as a selective barrier, controlling the flow of water and nutrients.

Question 11

Which of the following best describes the protoplast?

Accepted Answer

The protoplast is the living part of the cell, which includes the cell membrane, cytoplasm, and all the organelles within the cell, excluding the cell wall in plant cells.

Question 12

Which of the following describes the Casparian strip in plant roots?

Accepted Answer

The Casparian strip forms within the primary cell walls of endodermal cells in plant roots and is impregnated with suberin, not cutin, creating a barrier to regulate the flow of water and nutrients.

Question 13

Water potential is generally most negative in which of the following parts of a plant?

Accepted Answer

Water potential is generally most negative in the mesophyll cells of the leaf, which helps in pulling water upward from the roots through the xylem vessels due to the transpiration pull.

Question 14

Compared to a cell with few aquaporins in its membrane, a cell containing many aquaporins will have which of the following?

Accepted Answer

Aquaporins facilitate the passive transport of water across cell membranes. A cell with many aquaporins will allow water to move more rapidly across its membrane, increasing the rate of osmosis. This does not directly affect water potential or the rate of active transport, which requires energy.

Question 15

Which of the following defines the loss of water from the aerial parts of plants?

Accepted Answer

Transpiration is the process by which water vapor is lost from the aerial parts of plants, primarily through the stomata in the leaves.

Question 16

Under which of the following conditions would guttation be most likely to occur?

Accepted Answer

Guttation occurs when root pressure builds up and forces water out through special leaf tip structures called hydathodes. This typically happens when transpiration rates are low, such as at night, allowing root pressure to exceed the pull of transpiration.

Question 17

What is the overall charge on the cytoplasmic side of a plant cell plasma membrane?

Accepted Answer

The overall charge on the cytoplasmic side of a plant cell plasma membrane is negative. This is due to the presence of negatively charged molecules such as proteins and nucleic acids inside the cell, and the active transport mechanisms that maintain a higher concentration of positive ions outside the cell.

Question 18

Most of the water absorbed by a plant is used for what purpose?

Accepted Answer

Most of the water absorbed by a plant is used to replace water lost during transpiration, a process where water evaporates from the surface of leaves. This is a significant aspect of a plant's water management and is crucial for maintaining its physiological processes.

Question 19

Which process provides the main force driving water within xylem vessels?

Accepted Answer

Evaporation of water through the stomata (transpiration) creates a tension that pulls water up through the xylem vessels from the roots to the leaves.

Question 20

If you place a flaccid plant cell in pure water, which of the following will occur?

Accepted Answer

Water enters the cell because the flaccid cell has solutes and low water potential, causing osmosis to occur as water moves from an area of high water potential (pure water) to an area of low water potential (the flaccid cell).

Quiz 36: Transport in Vascular Plants