Deck 35: Transport in Plants

Question 1

What happens when a large amount of water enters a plant cell?

A) Entry of water increases as the water potential increases.
B) Entry of water is opposed by turgor pressure.
C) Water moves toward the region of more positive water potential.
D) Entry of water reduces the turgor pressure.
E) Entry of water causes increased active transport into the cell.

Answer 1

B

Question 2

Osmosis

A) requires ATP.
B) results in the bursting of plant cells placed in pure water.
C) can cause a cell to become turgid.
D) is independent of solute concentrations.
E) continues until the pressure potential equals the water potential.

Answer 2

C

Question 3

Which statement about proton pumping across the plasma membrane of plants is not true?

A) It requires ATP.
B) The region inside the membrane becomes positively charged with respect to the region outside.
C) It enhances the movement of K⁺ ions into the cell.
D) It pushes protons out of the cell against a proton concentration gradient.
E) It can drive the secondary active transport of negatively charged ions.

Answer 3

B

Question 4

In the xylem,

A) the products of photosynthesis travel down the stem.
B) living, pumping cells push the sap upward.
C) the driving force is in the roots.
D) the sap is often under tension.
E) the sap must pass through sieve plates.

Question 5

Which of the following processes can take place even without the presence of living cells?

A) Osmosis
B) Transpiration
C) Translocation
D) Active transport
E) Facilitated diffusion

Question 6

What would happen if the soil around a tall tree were contaminated by salt?

A) The tree would continue to grow just as it had before the salt contamination.
B) The tree would become stronger because of the increase of minerals in the soil.
C) The tree would require less water to maintain a water potential gradient.
D) The tree could die because the soil water potential would be lower than that of the root.
E) The tree would create more xylem to accommodate the extra mineral load.

Question 7

Which statement is not true?

A) The symplast consists of the interconnected cytoplasm of living cells.
B) Water can enter the stele without entering the symplast.
C) The Casparian strips prevent water from moving between endodermal cells.
D) The endodermis is a cell layer in the cortex.
E) Water can move freely in the apoplast without entering cells.

Question 8

The tendency for water to move toward greater solute concentration is an example of

A) active transport.
B) osmolarity.
C) diffusion.
D) reverse osmosis.
E) passive transport.

Question 9

Stomata

A) control the opening of guard cells.
B) release less water to the environment than do other parts of the epidermis.
C) open when CO₂ levels inside the leaf are high.
D) do not respond to light.
E) close when water is being lost at too great a rate.

Question 10

Which of the following is not part of the transpiration-cohesion-tension mechanism?

A) Water evaporates from the walls of mesophyll cells.
B) Removal of water from the xylem exerts a pull on the water column.
C) Water is remarkably cohesive.
D) The wider the tube, the greater the tension its water column can withstand.
E) At each step, water moves to a region with a more strongly negative water potential.

Question 11

Which statement about aquaporins is not true?

A) They are membrane transport proteins.
B) Water movement through aquaporins is always active.
C) The permeability of some aquaporins is subject to regulation.
D) They vary in abundance depending on environmental conditions.
E) They enable water to pass through the phospholipid bilayer without encountering a hydrophobic environment.

Question 12

The fibrous protein in sieve tube elements

A) may plug leaks when a plant is damaged.
B) clogs the sieve plates at all times.
C) never clogs the sieve plates.
D) serves no known function.
E) provides the driving force for transport in the phloem.

Question 13

In which of the following water potential conditions will water move from the root hairs through the cortex to the xylem?

A) Root hairs = 0, cortex = 0, xylem = 0
B) Root hairs = -1, cortex = -1, xylem = -1
C) Root hairs = -2, cortex = -1, xylem = 0
D) Root hairs = 0, cortex = +1, xylem = +2
E) Root hairs = 0, cortex = -1, xylem = -2

Question 14

Pure water under no applied pressure has a water potential of

A) +10.
B) +1.
C)
0)D) -1.
E) -10.

Question 15

A plant cell placed in distilled water will

A) expand until the osmotic potential reaches that of distilled water.
B) become more turgid until the osmotic potential reaches that of distilled water.
C) become less turgid until the osmotic potential reaches that of distilled water.
D) become more turgid until the pressure potential of the cell reaches its solute potential.
E) become less turgid until the pressure potential of the cell reaches the outside water potential.

Question 16

The movement of water in plants caused by differences in pressure potential is called

A) osmosis.
B) passive transport.
C) diffusion.
D) active transport.
E) bulk flow.

Question 17

Which statement about phloem transport is not true?

A) It takes place in sieve tubes.
B) It depends on mechanisms for loading solutes into the phloem at sources.
C) It stops if the phloem is killed by heat.
D) A high pressure potential is maintained in the sieve tubes.
E) At sinks, solutes are actively transported into sieve tube elements.

Question 18

Water potential

A) is the difference between the solute potential and the pressure potential.
B) is analogous to the air pressure in an automobile tire.
C) is the movement of water through a membrane.
D) determines the direction of water movement between cells.
E) is defined as 1.0 MPa for pure water under no applied pressure.

Question 19

Water tends to move into a cell that has

A) a high turgor pressure due to cell wall rigidity.
B) a high, positive water potential.
C) an interior solute concentration like that of distilled water.
D) a more negative water potential than its surroundings.
E) reached equilibrium.

Question 20

The wilting of plant tissue occurs when _______ is _______.

A) water potential; high
B) turgor pressure; high
C) interior solute concentration; high
D) osmotic potential; high
E) turgor pressure; low

Question 21

Parenchyma cells within the stele facilitate movement of minerals from the _______ into the _______.

A) cell wall; cytoplasm
B) cytoplasm; cell wall
C) cell wall; cell wall of the neighboring cell
D) cytoplasm; next cell's cytoplasm
E) cell wall; next cell's cytoplasm

Question 22

Pumping protons (H⁺) out of a cell can trigger the movement of

A) K⁺ out of the cell and Cl^- into the cell.
B) K⁺ into the cell and Cl^- out of the cell.
C) both K⁺ and Cl^- out of the cell.
D) both K⁺ and Cl^- into the cell.
E) K⁺ into the cell, with no movement of Cl^-.

Question 23

Where bulk flow occurs in plants, the liquid consists of

A) water and minerals.
B) water and organic molecules.
C) organic molecules only.
D) water only.
E) Both a and b

Question 24

Cell walls impregnated with water-repellent suberin are found in the cells of the

A) root hairs.
B) cortex.
C) endodermis.
D) pericycle.
E) tracheids.

Question 25

Water enters the xylem tissue from surrounding root cells via

A) active transport.
B) facilitated diffusion.
C) osmosis.
D) pressure pumping.
E) guttation.

Question 26

When the ion concentration inside root cells is higher than the concentration in the soil solution, ions in the soil solution can enter root cells by means of

A) active transport only.
B) simple diffusion only.
C) simple diffusion and facilitated diffusion.
D) facilitated diffusion and active transport.
E) simple diffusion and active transport.

Question 27

Plasmodesmata allow materials to move by a(n) _______ route.

A) apoplastic
B) symplastic
C) cohesive
D) bulk
E) electrical gradient

Question 28

Endodermal cells differ from other cells in the root in that they

A) lack a symplast region.
B) are nonselective with regard to solute uptake.
C) have a high rate of water transport.
D) are completely surrounded by a waxy layer.
E) prevent the apoplastic movement of water and ions.

Question 29

The facilitated diffusion of ions from the soil solution into root cells requires

A) that the concentration of ions at the root cells be the same outside and inside.
B) that the concentration of ions outside the root cells be lower than the concentration inside.
C) the expenditure of ATP.
D) specific channel proteins in the membranes.
E) cellular respiration.

Question 30

Most water moving through the apoplast from the soil into the stele cells first crosses a plasma membrane in the cells of the

A) root hairs.
B) cortex.
C) endodermis.
D) pericycle.
E) tracheids.

Question 31

The uptake of ions in plant cells is influenced by the

A) electrical gradient.
B) concentration gradient.
C) ionic balance.
D) pumping of H⁺.
E) All of the above

Question 32

Which of the following statements about aquaporins is true?

A) They are necessary to protect cells from toxins.
B) They are involved directly in mineral transport.
C) They increase water flow through cell membranes.
D) They prevent too much water from traveling between cells.
E) They contain transport proteins.

Question 33

The phenomenon of guttation is related to

A) active transport.
B) osmosis.
C) root pressure.
D) transpiration.
E) translocation.

Question 34

The Casparian strip is

A) a layer of endodermal cells.
B) a layer of epidermal cells.
C) the apoplast.
D) the symplast.
E) the waxy region of the endodermal cell walls.

Question 35

Which of the following is part of the apoplast?

A) Cell wall
B) Plasma membrane
C) Plasmodesma
D) Cytoplasm
E) Vacuole

Question 36

Mineral nutrients enter the plant body directly from the environment by means of uptake

A) through the roots.
B) by the leaves.
C) from digested food molecules.
D) into vascular tissue.
E) through the stems.

Question 37

The energy that drives water into root cells comes most directly from

A) ATP.
B) the sun.
C) NADPH⁺.
D) bulk flow.
E) chloroplasts.

Question 38

Which of the following statements about the apoplast (the transport route through intercellular spaces) is true?

A) Osmosis of water is not involved.
B) Movement of materials is regulated by membranes.
C) Water and solutes can move by bulk flow.
D) Plasmodesmata are involved.
E) Water and solutes enter the stele via this channel.

Question 39

Guttation is most commonly observed under conditions of _______ atmospheric humidity and _______ soil water.

A) high; plentiful
B) low; plentiful
C) high; little
D) low; little
E) varying; plentiful

Question 40

In order to transport K⁺ ions into their cells, plants

A) pump H⁺ out.
B) use the sodium-potassium pump.
C) pump K⁺ in.
D) pump water in.
E) Both b and c

Question 41

What is the process by which movement of K⁺ ions initiates stomatal closing?

A) Active transport into the guard cells
B) Active transport out of the guard cells
C) Active transport from one guard cell to another
D) Diffusion into the guard cells
E) Diffusion out of the guard cells

Question 42

Which property accounts for the movement of water upward through a narrow tube?

A) Cohesion of water molecules via hydrogen bonding
B) Negative water potential in the xylem
C) Active transport of water molecules
D) Passive osmosis of water following ion movement
E) Pumping of water into the phloem

Question 43

As a tree begins transpiring in the morning, tension pressure occurs first in the

A) leaves.
B) branches.
C) trunk.
D) roots.
E) All of the above

Question 44

In most plants, the stomata at night are

A) open to take in water.
B) open to take in CO₂.
C) closed to prevent water loss.
D) closed to prevent CO₂ loss.
E) closed to exclude O₂.

Question 45

The evaporative loss of water from the leaf is called

A) translocation.
B) transformation.
C) transportation.
D) transpiration.
E) transcention.

Question 46

The transpiration-cohesion-tension mechanism explains how

A) water is lost from leaf openings.
B) water is transported in the xylem.
C) water and minerals enter the root.
D) solutes are translocated within the phloem.
E) leaf epidermal cells minimize water loss.

Question 47

Which structure of the leaf minimizes water loss?

A) Cortex
B) Epidermis
C) Cuticle
D) Phloem
E) Xylem

Question 48

Per Scholander used _______ to measure tension in xylem sap.

A) a balloon in a bell jar
B) a water column
C) an aphid
D) a barometer
E) a pressure chamber

Question 49

Which of the following increases a plant's intake of CO₂ for photosynthesis?

A) Thick waxy cuticle
B) Loss of water vapor
C) Darkness
D) Electric imbalance
E) Open stomata

Question 50

Bulk water flow is stopped by

A) metabolic inhibitors.
B) closed stomata.
C) accumulation of K⁺.
D) blue light.
E) surface tension.

Question 51

To initiate stomatal opening, K⁺ ions

A) passively diffuse into guard cells.
B) passively diffuse out of guard cells.
C) are driven into guard cells by a charge gradient.
D) are actively transported out of guard cells.
E) bond to receptor sites on guard cell walls.

Question 52

Per Scholander placed plant stems in pressure chambers in order to measure

A) tension.
B) cohesion.
C) adhesion.
D) osmosis.
E) turgor.

Question 53

Cohesion is the tendency of water molecules to attract _______ molecules by means of _______ bonds.

A) other water; covalent
B) other water; hydrogen
C) cellulose; covalent
D) cellulose; hydrogen
E) lignin; covalent

Question 54

Which process makes the water potential in a leaf more negative?

A) The pressure placed on the leaf by the cuticle
B) The evaporation of water from mesophyll cells
C) The movement of water into the leaf by root pressure
D) The increased K⁺ pumped out of guard cells
E) The movement of water from the veins into the leaf

Question 55

Which of the following causes the root pressure that moves water upward in plant xylem?

A) Negative water potential in the xylem sap
B) High pressure potential of water in the soil
C) Movement of water from root cells into the soil
D) Active transport of minerals from soil to root cells
E) High atmospheric humidity

Question 56

If a stem is cut and the xylem sap is under tension,

A) xylem sap will spurt out.
B) xylem sap will stay at the cut surface.
C) air will be pulled into the xylem.
D) the cut surface will form bubbles if placed under water.
E) xylem sap will run out if placed under water.

Question 57

In which of the following conditions do plants close their stomata?

A) Bright sunlight
B) Water stress
C) High CO₂
D) Lack of wind
E) Warm temperatures

Question 58

Stomata begin to open when K⁺

A) becomes concentrated, water enters guard cells, and the cells become turgid.
B) leaves guard cells and they become less turgid.
C) enters guard cells and they become less turgid.
D) leaves guard cells and they become turgid.
E) reaches equilibrium in guard cells and their surroundings.

Question 59

The unbroken column of water from the roots to the highest leaves is kept intact by

A) tension.
B) transpiration.
C) atmospheric pressure.
D) cohesion.
E) evaporation.

Question 60

Mineral ions move in the xylem

A) passively.
B) by means of active transport.
C) by osmosis.
D) because of root pressure.
E) by means of the pumping action of various cells.

Question 61

Plant physiologists can obtain pure phloem sap from individual phloem cells by

A) using tiny drills and capillary pipettes.
B) collecting material from aphid stylets.
C) obtaining liquids oozing from cut stem surfaces.
D) collecting droplets formed by guttation.
E) gathering the mycorrhizal fungi for subsequent analysis.

Question 62

The active transport of sucrose molecules from a leaf's apoplast to its phloem requires that the sucrose be cotransported with

A) H⁺.
B) amino acids.
C) K⁺.
D) Cl^-.
E) water.

Question 63

Cells in the leaf release abscisic acid in response to

A) an excessively negative water potential.
B) a reduction in CO₂.
C) the reduction in light at night.
D) an increase of Cl^- in the stomata.
E) an increase in K⁺ in the stomata.

Question 64

Water enters a plant mainly through its _______.

Question 65

Water moves toward regions of more _______ water potential.

Question 66

Cell walls and spaces between cells make up a compartment called the _______; the continuous cytoplasm of living cells connected by plasmodesmata is called the _______.

Question 67

Which of the following is a function of abscisic acid?

A) Storage of CO₂ for daytime use
B) Reduction of water loss
C) Opening of stomata
D) Increased H⁺ pumping in guard cells
E) Lowering of pH

Question 68

When osmotic _______ becomes more negative inside a cell, water moves into the cell passively by osmosis.

Question 69

According to the pressure flow model for translocation,

A) sugar concentration is highest near the sink area.
B) water enters the sieve tube by osmosis.
C) sugar is transported out of the sieve tubes near the source area.
D) osmosis accomplishes the bulk flow of water and nutrients.
E) little ATP expenditure is required.

Question 70

Minerals taken up in their ionic form are moved into root cells against their concentration gradient by the process of _______ transport.

Question 71

The effect of increasing dissolved solutes is to make the solute potential (more/less) _______ negative.

Question 72

Sugars move from the sieve tubes into the plant's tissue

A) by diffusion.
B) via the apoplast.
C) by active transport.
D) by osmosis.
E) via translocation.

Question 73

The pressure flow model of translocation depends entirely on the existence of mechanisms for loading sugars into phloem at the _______ regions and for unloading them at the _______ regions.

A) sink; sink
B) sink; source
C) source; source
D) source; sink
E) source; source or sink

Question 74

The movement of substances between living cells of a plant occurs through _______.

Question 75

When water moves outside cells, the movement is (regulated/unregulated) _______.

Question 76

Sugars pass from cell to cell in the leaf starting in the _______ of the mesophyll; they move through the _______ of other cells and finally pass into the _______ of the sieve tube element.

A) symplast or apoplast; symplast; symplast
B) apoplast; apoplast; apoplast
C) symplast; symplast or apoplast; symplast
D) apoplast; symplast; symplast
E) apoplast; symplast; apoplast

Question 77

When a tree is girdled, the bark swells in the region _______ the girdle, and the _______ die before the rest of the tree.

A) below; roots
B) below; branches
C) below; leaves
D) above; roots
E) above; branches

Question 78

Which technique allowed researchers to conclude that the fibrous proteins in sieve tube elements are normally dispersed and obstruct sieve plates only in response to cell damage?

A) Analyzing phloem sap extruded from aphid stylets
B) Freezing phloem tissue before cutting and examining it
C) Watering a plant before cutting and examining it
D) Using patch clamping to examine sieve plates
E) Exposing plants to blue light before examination

Question 79

According to the pressure flow model, during fruit development, photosynthesizing leaves are the _______ and the fruit are the _______.

A) sink; sink
B) sink; source
C) source; source
D) source; sink
E) source; source or sink

Question 80

When sugars are actively transported into a cell, turgor pressure inside that cell

A) does not change, because sugar concentration has no effect on turgor pressure.
B) increases, because sugar concentration directly affects turgor pressure.
C) increases, because water enters and affects turgor pressure.
D) decreases, because water exits and affects turgor pressure.
E) decreases, because sugar concentration directly affects turgor pressure.