Question 1

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 a layer of cells in the root that functions as the innermost layer of the cortex. It is important in regulating the movement of water and solutes into the central cylinder of the root. The presence of the Casparian strip, a water-impermeable ring of wax in the cell walls, forces water to pass through the plasma membranes of the endodermal cells, meaning that any water molecule passing through the endodermal cell would have to pass through a living cell just once.

Question 2

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

Accepted Answer

The cohesion of water molecules, a negative water potential, the active transport of solutes, and bulk flow from source to sink are all important components of the long-distance transport process in plants. Root parenchyma is not directly involved in this process. Therefore, the correct choice is C - I, II, IV, and V.

Question 3

One is most likely to see guttation in small plants when the ________.

Accepted Answer

Guttation occurs when root pressure exceeds transpiration pull, causing the water to exit through the leaf tips. This is more common in small plants with higher root pressure. Transpiration rates, weather conditions, and mineral absorption by roots do not directly affect guttation.

Question 4

The protoplast consists of ________.

Accepted Answer

The protoplast is the living part of the cell, which includes the cell membrane, cytoplasm, and nucleus, but excludes the cell wall.

Question 5

Transpiration in plants requires ________.
I.adhesion of water molecules to cellulose
II.cohesion between water molecules
III.evaporation of water molecules
IV.active transport through xylem cells
V.transport through tracheids

Accepted Answer

Transpiration involves adhesion (I) and cohesion (II) of water molecules, evaporation (III) from leaf surfaces, and transport through tracheids (V). Active transport (IV) is not involved in xylem transport.

Question 6

In plant roots, the Casparian strip ________.

Accepted Answer

The Casparian strip is a band of cell wall material that encircles the cells of the endodermis in plant roots. It is impermeable to water and minerals and forces them to pass through a cell membrane before entering the stele. This allows the plant to regulate the uptake of minerals and water into the plant. Therefore, option D is the correct answer.

Question 7

The value for Ψ in root tissue was found to be -0.15 MPa. If you take the root tissue and place it in a 0.1 M solution of sucrose (Ψ = -0.23 MPa), the net water flow would ________.

Accepted Answer

Water moves from areas of higher water potential to areas of lower water potential. Since the water potential of the root tissue (-0.15 MPa) is higher than that of the sucrose solution (-0.23 MPa), water will flow from the tissue into the sucrose solution.

Question 8

Bulk flow is much faster than diffusion or active transport. Peak velocities in the transport of xylem sap can range from ________ for trees with wide vessel elements.

Accepted Answer

Peak velocities in the transport of xylem sap for trees with wide vessel elements can range from 15-45 m/hr, which is significantly faster than diffusion or active transport.

Question 9

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.fibrous arrangement of the roots

Accepted Answer

Root hairs, mycorrhizae, and a fibrous arrangement of roots all increase the surface area for water absorption. Root hairs extend the root surface, mycorrhizae are symbiotic fungi that enhance nutrient and water uptake, and a fibrous root system increases the root surface area. The endodermis does not contribute to surface area but regulates water and nutrient flow into the plant.

Question 10

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. This does not happen to plant cells, because ________.

Accepted Answer

Plant cells have cell walls, which provide pressure to counteract the pressure of incoming water. This pressure, known as turgor pressure, helps maintain the shape and structure of the plant cell even in a hypotonic solution.

Question 11

Compared to a cell with few aquaporins in its membrane, a cell containing many aquaporins will ________.

Accepted Answer

Aquaporins are channels that facilitate the movement of water across the cell membrane. If a cell has more aquaporins, there will be more channels available for water to cross the membrane, leading to a faster rate of osmosis. This means that water will move more quickly from high to low concentration, resulting in a faster equalization of water concentration on both sides of the membrane. A higher water potential (C) would mean that the cell has a greater tendency to take up water, but this is not necessarily related to the number of aquaporins in the membrane. Active transport (D) is a completely different process that is not related to osmosis or the presence of aquaporins.

Question 12

If ΨP = 0.3 MPa and ΨS = -0.45 MPa, the resulting Ψ is ________.

Accepted Answer

To calculate the resulting Ψ, we need to add ΨP and ΨS:

Ψ = ΨP + ΨS

Substituting the given values, we get:

Ψ = 0.3 MPa + (-0.45 MPa)
Ψ = -0.15 MPa

Therefore, the resulting Ψ is -0.15 MPa. The correct answer is C).

Question 13

During the nighttime, due to lack of transpiration, the water potential within the vascular cylinder ________.

Accepted Answer

During the nighttime, transpiration is minimal, leading to the accumulation of minerals in the vascular cylinder, which lowers the water potential.

Question 14

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

Accepted Answer

This observation highlights a key limitation of root pressure as the principal mechanism of water transport in the xylem. Over long distances, the force of root pressure is not sufficient to overcome the force of gravity and push water up to the leaves. This suggests that there must be an additional mechanism, such as transpiration pull, that can generate the necessary force to move water all the way up from the roots to the leaves. The other observations listed are not necessarily incompatible with root pressure as the principal mechanism of water transport in the xylem.

Question 15

Loss of water from the aerial parts of plants is called ________.

Accepted Answer

Loss of water from the aerial parts of plants is called transpiration.

Question 16

How does a flaccid cell differ from a turgid cell?

Accepted Answer

A flaccid cell has lower pressure potential than a turgid cell. In a turgid cell, the cell wall is fully expanded due to the movement of water into the cell, resulting in high pressure potential. In contrast, a flaccid cell has lost some of its water, and the cell wall is not fully expanded, resulting in lower pressure potential.

Question 17

What is the main force by which most of the water within xylem vessels moves toward the top of a tree?

Accepted Answer

The main force by which most of the water within xylem vessels moves toward the top of a tree is the evaporation of water through stoma. This process is known as transpiration and creates a negative pressure, or tension, within the xylem that pulls water up from the roots. This process is also known as the transpiration-cohesion-tension mechanism.

Question 18

Most of the water taken up by a plant is ________.

Accepted Answer

Most of the water absorbed by plants is lost to the atmosphere through the process of transpiration, which is the evaporation of water from plant leaves.

Question 19

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

Accepted Answer

The cytoplasmic side of a plant cell plasma membrane has a negative charge due to the presence of negatively charged ions, such as proteins and nucleic acids, inside the cell.

Question 20

If you place flaccid plant cells in pure water, water ________ into cell because it has ________.

Accepted Answer

Water enters the cell because the cell has solutes and a lower water potential compared to pure water, causing water to move into the cell by osmosis.

Quiz 36: Resource Acquisition and Transport in Vascular Plants