Deck 35: Transport in Plants

Question 1

What is the solute potential (ψ_S) of a living plant cell in a living leaf that is not wilted relative to the fluids surrounding the cell?

A)typically lower
B)typically higher
C)varies widely from higher to lower
D)typically about the same

Answer 1

A

Question 2

Suppose you discover a mutant plant that CANNOT actively transport solutes across the tonoplast. How will this plant differ from a wild-type plant?

A)The plant will generally be like a normal plant.
B)The plant will wilt easily.
C)The plant will not have roots.
D)The plant will not have leaves.

Answer 2

B

Question 3

How would water flow if the ψ of surrounding soil is higher than that in living root epidermal cells?

A)Water would leave the root cells, making them flaccid.
B)Water would leave the root cells, making them turgid.
C)Water would enter the root cells, making them flaccid.
D)Water would enter the root cells, making them turgid.

Answer 3

D

Question 4

Which of the following should you expect to find for a living plant cell in a living plant?

A)a cytoplasm that is much more positively charged than the fluid outside the cell
B)a cytoplasm that is much more negatively charged than the fluid outside the cell
C)a cytoplasm that is slightly more negatively charged than the fluid outside the cell
D)a cytoplasm that is slightly more positively charged than the fluid outside the cell

Question 5

What does tonoplast refer to?

A)the plant nuclear envelope
B)the cell wall
C)a chloroplast
D)the vacuolar membrane

Question 6

Consider a living plant cell in a living leaf that has higher water potential than the fluids surrounding the cell. What would happen to the water?

A)There would be no net flow of water into or out of the cell.
B)There would be a gain of water by the cell only if the cell's pressure potential is low enough.
C)There would be a net flow of water out of the cell.
D)There would be a gain of water by the cell only if the cell's pressure potential is high enough.

Question 7

Which term best describes the movement of NH₄⁺ ions into a cell down an electrochemical gradient?

A)a symport
B)passive diffusion
C)facilitated diffusion
D)active transport

Question 8

What does water potential refer to?

A)a relative value that is defined in reference to distilled water at atmospheric pressure of 10 MPa
B)a relative value that is defined in reference to pure water at atmospheric pressure of 10 MPa
C)a relative value that is defined in reference to pure water at atmospheric pressure of 0 MPa
D)a relative value that is defined in reference to distilled water at atmospheric pressure of 0 MPa

Question 9

What is the pressure potential (ψ_P) of a living plant cell in a living leaf that is not wilted relative to that in the fluids surrounding the cell?

A)typically about the same
B)varies widely from higher to lower
C)typically higher
D)typically lower

Question 10

Which of the following best describes aquaporins?

A)They are channel proteins for water.
B)They are carrier proteins for water.
C)They are channel proteins for solutes.
D)They are carrier proteins for water and solutes.

Question 11

What are the primary aspects of the process used by a tall tree to move water to the leaves at the top of the tree?

A)positive pressure from roots and cohesion
B)cohesion and evaporation
C)capillary action and pumps
D)capillary action and positive pressure from roots

Question 12

Which plant organelle stores solutes and plays a major role in maintaining turgor pressure?

A)chloroplast
B)mitochondrion
C)vacuole
D)cell wall

Question 13

Which term best describes the structure that is necessary for facilitated diffusion?

A)a receptor protein
B)a pore
C)a signal protein
D)a carrier protein

Question 14

Which term best describes the movement of ions and large molecules across membranes via transport proteins against their concentration gradient?

A)passive diffusion
B)a symport
C)facilitated diffusion
D)active transport

Question 15

Suppose a living plant cell has ψ_P = 0.4 MPa and ψ_S = -0.5 MPa. Suppose also that the plant cell is placed into a beaker filled with a solution for which ψ = ψ_S = -0.9 MPa. What will the cell then do?

A)It will take up water until within the cell ψ_P = -ψ_S.
B)It will lose water until its ψ_S = its ψ_P.
C)It will lose water until its ψ = ψ of the solution.
D)It will take up water until it bursts.

Question 16

Which of the following best describes the process by which individual plant cells typically gain or lose water?

A)symport
B)guttation
C)osmosis
D)facilitated diffusion

Question 17

Suppose that a living plant cell is placed in a beaker with a solution that has a ψ value lower than the ψ value of the plant cell. What will happen to the plant cell?

A)It will lose water until its ψ_S = its ψ_P.
B)It will take up water until within the cell ψ_P = -ψ_S.
C)It will take up water until its ψ = ψ_S of the solution.
D)It will lose water until its ψ = ψ of the solution.

Question 18

Suppose that a living plant cell is placed in a beaker with pure water. How long will it take up water?

A)until it is flaccid
B)until it is turgid
C)until it is shrunken
D)until it is plasmolysed

Question 19

Suppose a living plant cell has ψ = ψ_S = -0.5 MPa. Also suppose that the plant cell is placed into a beaker filled with a solution for which ψ = 0. What will the cell then do?

A)It will lose water until its ψ_S = its ψ_P.
B)It will take up water until within the cell ψ_P = -ψ_S.
C)It will take up water until its ψ_S = ψ_S of the solution.
D)It will take up water until it bursts.

Question 20

Which Greek letter is typically used to represent water potential?

A)Greek letter γ
B)Greek letter α
C)Greek letter π
D)Greek letter ψ

Question 21

What is the evaporation of water from plant tissues called?

A)guttation
B)root pressure
C)transpiration
D)cohesion-tension

Question 22

Xylem sap is moved from the root system into what other structure in the plant body?

A)the tonoplast system
B)the shoot system
C)the taproots
D)the trichomes

Question 23

Which of the following characterizes the symplastic pathways in the root?

A)the water moves into and through living cells and is moving through the cytoplasm
B)the water moves into and through living cells and is moving through the cell wall
C)the water moves into and through nonliving cells and is moving through the cytoplasm
D)the water moves into and through nonliving cells and is moving through the cell wall

Question 24

Which route of water absorption is inhibited by the Casparian strip?

A)the apoplastic pathway
B)the transplastic pathway
C)the symplastic pathway
D)the transmembrane pathway

Question 25

Which of the following characterizes the apoplastic pathways in the root?

A)the water moves through living regions but in the endodermis it must pass through the cell wall
B)the water moves through nonliving regions but in the endodermis it must pass through the cell wall
C)the water moves through living regions but in the endodermis it must pass through the cytoplasm
D)the water moves through nonliving regions but in the endodermis it must pass through the cytoplasm

Question 26

Suppose two living plant cells are in contact with each other such that water, but NOT solutes, can pass between them. Also suppose that the cells have the same water potential, and that one cell has ψ_P = 0.3 MPa and ψ_S = -0.5 MPa, while the other cell has ψ_S = -0.3 MPa. What is the ψ_P of the second cell?

A)ψ_P = -0.8 MPa
B)ψ_P = 0.1 MPa
C)ψ_P = 0.5 MPa
D)ψ_P = 0.8 MPa

Question 27

According to the cohesion-tension mechanism of water transport, why does cohesion occur?

A)because water molecules tend to form hydrogen bonds with each other
B)because water is pushed into the xylem by bulk flow
C)because waxy coatings on the insides of xylem keep water molecules together in the xylem
D)because evaporation removes water from the leaves

Question 28

Which term best describes the typical movement of xylem sap from roots to shoot parts?

A)facilitated diffusion
B)symport
C)osmosis
D)bulk flow

Question 29

What route is being followed by water that moves through living cells in a root?

A)the symplastic and epidermal pathways
B)the transmembrane and apoplastic pathways
C)the transmembrane and symplastic pathways
D)the apoplastic and epidermal pathways

Question 30

What is the waxy substance suberin typically associated with?

A)root hairs
B)tonoplasts
C)endodermis
D)pericycle

Question 31

Which sentence best describes how mineral ions are absorbed by plants?

A)They are moved into the symplast via facilitated diffusion.
B)They are moved into the apoplast via bulk flow.
C)They are moved into the symplast via active transport.
D)They are moved into the apoplast via facilitated diffusion.

Question 32

What is the ψ_P of a living plant cell that has ψ = -0.2 MPa and ψ_S = -0.4 MPa?

A)ψ_P = -0.6 MPa
B)ψ_P = 0.08 MPa0
C)ψ_P = 0.2 MPa
D)ψ_P = 0.5 MPa

Question 33

What route is being followed by water that moves through nonliving regions of a root, such as air spaces in root tissue?

A)the apoplastic, transmembrane, and epidermal pathways
B)the symplastic, transmembrane, and transepidermal pathways
C)the transmembrane, epidermal, and transepidermal pathways
D)the apoplastic, transmembrane, and symplastic pathways

Question 34

Which is the most widely accepted and supported model for explaining the movement of xylem sap?

A)the transpiration mechanism
B)the osmosis mechanism
C)the pressure flow mechanism
D)the cohesion-tension mechanism

Question 35

What is the principal driving force for movement of water into and through the plant shoot?

A)upward pressure as sugar is forced into the roots
B)pumping by the xylem cells
C)passive transport
D)transpirational pull

Question 36

Many plants wind up with a Na⁺ concentration that is considerably lower than that of the surrounding soil. What plays a key role in allowing for such a difference to exist?

A)endodermis
B)tonoplast
C)aquaporin
D)water potential

Question 37

Which phrase best describes the exodermis?

A)the outer layer of roots, including root hairs
B)the above-ground continuation of the endodermis
C)the substitute for the endodermis in gymnosperms
D)found in the roots of most flowering plants

Question 38

What is the fate of the majority of the water in xylem sap?

A)It evaporates into the air.
B)It is used to make sugars.
C)It is used in capturing light energy.
D)It becomes part of new plant cells.

Question 39

Which of the following best describes the mechanism(s) by which water can move inside a root?

A)apoplastic, transmembrane, and symplastic pathways
B)transmembrane and symplastic pathways
C)transmembrane pathway
D)apoplastic pathway

Question 40

What drives the process of transpiration?

A)upward pressure as sugar is forced into the roots
B)evaporation
C)pumping by the xylem cells
D)passive transport

Question 41

Which of the following are found on either side of a plant stoma?

A)guard cells
B)trichomes
C)leaves
D)root hairs

Question 42

Which ion is pumped out of guard cells in order to increase their turgidity?

A)H⁺
B)Ca²⁺
C)Na⁺
D)K⁺

Question 43

What needs to happen to the K⁺ concentration in guard cells for the stomata to open?

A)It needs to fluctuate.
B)It needs to remain unchanged.
C)It needs to decrease.
D)It needs to increase.

Question 44

Under which conditions would essentially no transpiration be expected to occur?

A)near freezing air temperature
B)hot air temperature and no winds
C)brisk winds
D)100% relative humidity

Question 45

What generally causes stomata to close?

A)nightlight
B)daylight
C)high moisture
D)high K⁺ content

Question 46

What is the state of stomata in CAM plants, such as cacti?

A)They are nearly always open.
B)They are open during the day and are closed during the night.
C)They are almost never open.
D)They are open during the night and are closed during the day.

Question 47

What has the strongest effect on whether stomata are open or closed?

A)O₂ concentration
B)CO₂ concentration
C)light
D)ion concentrations in the xylem

Question 48

How far are most leaf cells from a xylem vein?

A)2.0 centimetres
B)1.0 centimetre
C)0.5 millimetres
D)50 micrometres

Question 49

Which of the following were used in studies to test and support the hypothesis that high pressure forces phloem sap to flow?

A)radiolabelled sugars
B)radiolabelled hormones
C)aphids
D)vacuum chambers

Question 50

What is the main form in which sugars are transported in the phloem sap?

A)starch
B)fructose
C)lactose
D)sucrose

Question 51

What generally causes stomata to open?

A)the release of abscisic acid by the roots
B)a drop in CO₂ concentration in leaf air spaces
C)an exposure to red light
D)a drop in O₂ concentration in leaf air spaces

Question 52

Which ion is pumped into guard cells in order to make them more flaccid?

A)Na⁺
B)Ca²⁺
C)K⁺
D)H⁺

Question 53

Which of the following describes the state of stomata in most plants?

A)They open during the night and close during the day.
B)They are nearly always open.
C)They are almost never open.
D)They are open during the day and close during the night.

Question 54

How would an air temperature rise of 10°C typically affect evaporation from leaves?

A)It would mostly eliminate evaporation.
B)It would double the rate of evaporation.
C)It would triple the rate of evaporation.
D)It would quadruple the rate of evaporation.

Question 55

What is the general term for long-distance transport of substances in plants?

A)osmosis
B)translocation
C)pressure flow
D)cohesion-tension

Question 56

Theoretically, based on the cohesion-tension mechanism, what should be the maximum height for the tallest trees?

A)about 3 m
B)about 50 m
C)about 75 m
D)about 130 m

Question 57

What is the principal driving force for guttation?

A)pumping by the xylem cells
B)sunlight
C)passive transport
D)root pressure

Question 58

Which ion plays the most prominent role in the opening and closing of stomata?

A)Cl-
B)K⁺
C)Na⁺
D)Ca²⁺

Question 59

Which of the following has a major effect on the rate of transpiration?

A)soil minerals
B)growth rate
C)air temperature
D)predation

Question 60

What is the major cost to plants for having cuticle-covered epidermis in the shoot system to reduce water loss?

A)reduced oxygen uptake
B)reduced nitrogen uptake
C)reduced carbon dioxide uptake
D)reduced potassium uptake

Question 61

Match each term or phrase with the letter of the associated plant tissue. Each letter may be used once, more than once, or not at all.
a.xylem
b.phloem
c.both xylem and phloem
d.neither xylem nor phloem
companion cells

Question 62

What is the water potential of phloem relative to the water potential of the surrounding xylem?

A)lower
B)higher
C)about the same
D)exactly the same

Question 63

Match each term or phrase with the letter of the associated plant tissue. Each letter may be used once, more than once, or not at all.
a.xylem
b.phloem
c.both xylem and phloem
d.neither xylem nor phloem
trichomes

Question 64

How does loading of most carbohydrates into companion cells at a source occur?

A)by diffusion of water from the xylem
B)by osmosis
C)by active transport
D)by proton pumping

Question 65

Match each term or phrase with the letter of the associated plant tissue. Each letter may be used once, more than once, or not at all.
a.xylem
b.phloem
c.both xylem and phloem
d.neither xylem nor phloem
bulk flow

Question 66

Explain the process that occurs when a stoma goes from closed to open.

Question 67

How do companion cells load most of the carbohydrates into sieve tube members?

A)by symport
B)through carrier proteins
C)through plasmodesmata
D)by antiport

Question 68

Where is phloem sap moved to?

A)to the root system
B)to sinks
C)to the shoot system
D)to sources

Question 69

Match each term or phrase with the letter of the associated plant tissue. Each letter may be used once, more than once, or not at all.
a.xylem
b.phloem
c.both xylem and phloem
d.neither xylem nor phloem
primary transport of ions from leaves

Question 70

Which term best describes the process by which sucrose is moved into a cell against its concentration gradient while at the same time, protons are moved into a cell with their concentration gradient?

A)facilitated diffusion
B)a symport
C)an antiport
D)active transport

Question 71

Match each term or phrase with the letter of the associated plant tissue. Each letter may be used once, more than once, or not at all.
a.xylem
b.phloem
c.both xylem and phloem
d.neither xylem nor phloem
primary transport of water from roots

Question 72

Match each term or phrase with the letter of the associated plant tissue. Each letter may be used once, more than once, or not at all.
a.xylem
b.phloem
c.both xylem and phloem
d.neither xylem nor phloem
cohesion-tension mechanism

Question 73

Match each term or phrase with the letter of the associated plant tissue. Each letter may be used once, more than once, or not at all.
a.xylem
b.phloem
c.both xylem and phloem
d.neither xylem nor phloem
stomata

Question 74

Explain the processes of phloem loading and unloading in a flowering plant.

Question 75

Match each term or phrase with the letter of the associated plant tissue. Each letter may be used once, more than once, or not at all.
a.xylem
b.phloem
c.both xylem and phloem
d.neither xylem nor phloem
transport of sugars

Question 76

What is the most widely accepted and supported model for explaining the movement of phloem sap in flowering plants?

A)the translocation mechanism
B)the pressure-flow mechanism
C)the transpiration mechanism
D)the cohesion-tension mechanism

Question 77

When solutes are unloaded from phloem, what happens to water?

A)It is pumped out of the phloem by active transport.
B)It is pumped into the phloem by active transport.
C)It leaves the xylem by osmosis.
D)It leaves the phloem by osmosis.

Question 78

Match each term or phrase with the letter of the associated plant tissue. Each letter may be used once, more than once, or not at all.
a.xylem
b.phloem
c.both xylem and phloem
d.neither xylem nor phloem
transport of hormones from growing shoot tips

Question 79

Which phrase best describes "honeydew"?

A)phloem sap leaving the anus of an aphid
B)phloem sap harvested as syrup
C)xylem sap separated from syrup
D)xylem sap forced out of the margins of leaves

Question 80

Match each term or phrase with the letter of the associated plant tissue. Each letter may be used once, more than once, or not at all.
a.xylem
b.phloem
c.both xylem and phloem
d.neither xylem nor phloem
dead cells throughout conducting portions