Chapter 36 Questions

Question 1

A fellow student brought in a leaf to be examined. The leaf was dark green, thin, had stomata on the lower surface only, and had a total surface area of ten square meters. Where is the most likely environment where this leaf was growing?

a. a tropical rain forest
b. an oasis within a grassland
c. a large, still pond
d. the floor of a deciduous forest

Answer 1

a. a tropical rain forest

Question 2

Why do most angiosperms have alternate phyllotaxy, with leaf emergence at an angle of 137.5 degrees compared to leaves above and below?

a. to allow maximum exposure to light and to reduce shading of lower leaves
b. to allow maximum exposure to light
c. to promote a leaf area index above 8
d. to reduce shading of lower leaves

Answer 2

a. to allow maximum exposure to light and to reduce shading of lower leaves

Question 3

A plant developed a mineral deficiency after being treated with a fungicide. What is the most probable cause of the deficiency?

a. Active transport of minerals was inhibited.
b. Mycorrhizal fungi were killed.
c. The genes for the synthesis of transport proteins were destroyed.
d. Mineral receptor proteins in the plant membrane were not functioning.

Answer 3

b. Mycorrhizal fungi were killed.

Question 4

The apoplast in plant tissues consists of ___.

a. cell walls, plasma membrane, and cytosol
b. cell walls, extracellular spaces, and vessel elements
c. cell walls, extracellular spaces, and plasmodesmata
d. vessel elements, plasmodesmata, and extracellular spaces

Answer 4

b. cell walls, extracellular spaces, and vessel elements

Question 5

Which of the following ions play the primary role in basic transport processes in plant cells?

a. K+
b. H+
c. Ca+2
d. Na+

Answer 5

b. H+

Question 6

Which of the following would be least likely to affect osmosis in plants?

a. receptor proteins in the membrane
b. aquaporins
c. a difference in water potential
d. a difference in solute concentrations

Answer 6

a. receptor proteins in the membrane

Question 7

How does a flaccid cell differ from a turgid cell?

a. A flaccid cell has higher pressure potential.
b. A flaccid cell has higher solute potential.
c. A flaccid cell has lower solute potential.
d. A flaccid cell has lower pressure potential.

Answer 7

d. A flaccid cell has lower pressure potential.

Question 8

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

a. have a faster rate of active transport
b. have a lower water potential
c. have a higher water potential
d. have a faster rate of osmosis

Answer 8

d. have a faster rate of osmosis

Question 9

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
a. I, II, IV, and V
b. I, III, IV, and V
c. I, II, III, and V
d. II, III, IV, and V

Answer 9

a. I, II, IV, and V

Question 10

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
a. I, II, III, and IV
b. I, III, and IV
c. I, II, and IV
d. II and III

Answer 10

b. I, III, and IV

Question 11

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 more. This living cell would be a part of which structure?

a. the roof cortex
b. the endodermis
c. a guard cell
d. the root epidermis

Answer 11

b. the endodermis

Question 12

In plant roots, the Casparian strip ___.

a. aids in the uptake of nutrients
b. ensures that all water and dissolved substances must pass through a cell membrane before entering the stele
c. provides energy for the active transport of minerals into the stele from the cortex
d. ensures that all minerals are absorbed from the soil in equal amounts

Answer 12

b. ensures that all water and dissolved substances must pass through a cell membrane before entering the stele

Question 13

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
a. I, III, IV, and V
b. I, II, IV, and V
c. I, II, III, and IV
d. I, II, III, and V

Answer 13

d. I, II, III, and V

Question 14

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

a. xylem vessels in roots
b. xylem vessels in leaves
c. mesophyll cells of the land
d. cells of the root cortex

Answer 14

c. mesophyll cells of the land

Question 15

Which one of the following ions plays a critical role in the opening and closing of stomata?

a. Na+
b. K+
c. H+
d. Ca+2

Answer 15

b. K+

Question 16

Which of the following primarily enters a plant somewhere other than through the roots?

a. carbon dioxide
b. potassium
c. water
d. nitrogen

Answer 16

a. carbon dioxide

Question 17

Ignoring all other factors, what kind of day would result in the fastest delivery of water and minerals to the laves of an oak tree?

a. a cool, dry day
b. a warm, humid day
c. a very hot, dry, windy day
d. a cool, humid day

Answer 17

c. a very hot, dry, windy day

Question 18

Plants adapted to arid environments are referred to as ___.

a. xerophytes
b. halophytes
c. psilophytes
d. mesophytes

Answer 18

a. xerophytes

Question 19

Arrange the following five events in an order that explains the mass flow of materials in the phloem.

1. Water diffuses into the sieve tubes.
2. Leaf cells produce sugar by photosynthesis.
3. Solutes are actively transported into sieve tubes
4. Sugar is transported from the cell to cell in the leaf.
5. Sugar moves down the stem.
   a. 2, 4, 3, 1, 5
   b. 1, 2, 3, 4, 5
   c. 4, 2, 1, 3, 5
   d. 2, 4, 1, 3, 5

Answer 19

a. 2, 4, 3, 1, 5

Question 20

Which of the following statements about the movement of water and inorganic nutrients in plants is true?

a. Water and nutrients move from the roots to the leavesvia the stem or trunk.
b. Water and nutrients move from the leaves to the roots via the stem or trunk.
c. Water and nutrients can move either from leaves to roots or from roots to leaves via the stem or trunk.
d. Water and nutrients are taken up by the roots and move symplastically by active transport to leaves.
e. Water and nutrients are pumped from the roots to the leaves via a proton pump.

Answer 20

a. Water and nutrients move from the roots to the leavesvia the stem or trunk.

Question 21

About ____% of a plant’s water escapes through the stomata, although the stomata account for just ____% of the external leaf surface.

a. 75; 10
b. 75; 1–2
c. 95; 10
d. 95; 1–2

Answer 21

d. 95; 1–2

Question 22

The basis of the pull generated by transpiration in the xylem is ____.

a. positive root pressure from differences in solute potential between soil and root.
b. positive pressure generated by the shrinking in diameter of the trunk or stem.
c. negative pressure at the air-water interface in the leaf.
d. pressure created by proton pumping of stomatal guard cells.
e. adhesion of water molecules to xylem cell walls.

Answer 22

c. negative pressure at the air-water interface in the leaf.

Question 23

Which reflects the correct relationship of water potentials for a typical tree on a sunny day?

a. leaf Ψ < trunk Ψ < soil Ψ
b. outside air Ψ > leaf c. mesophyll Ψ < root Ψ
c. leaf Ψ > trunk Ψ > soil Ψ
d. soil Ψ < root Ψ > leaf Ψ
e. none of the above

Answer 23

a. leaf Ψ < trunk Ψ < soil Ψ

Question 24

Water can follow two pathways in plants, apoplastic and symplastic. How do these pathways differ?

a. The apoplastic route is for water; the symplastic route is for nutrients.
b. The apoplastic route is entirely external to cell membranes; the symplastic route is inside of cells.
c. The apoplastic route is for nutrients; the symplastic route is for water.
d. The apoplastic route is used in phloem; the symplastic route is used in xylem.

Answer 24

b. The apoplastic route is entirely external to cell membranes; the symplastic route is inside of cells.

Question 25

Which of the following is a benefit of positioning and aligning leaves relative to one another?

a. A layer of still air can be created under the leaves, raising the O2 concentration found there.
b. More water can be lost from the surface of the leaves during the day.
c. Proper positioning can allow more light down to the lower leaves on the plant.
d. Certain arrangements can allow the plant to maximize its leaf area index (LAI).
e. On hot sunny days, horizontally aligned leaf blades tend to be kept cooler.

Answer 25

c. Proper positioning can allow more light down to the lower leaves on the plant.

Question 26

Which of the following is not a way that plants use sunlight?

a. to help sense how to best align their leaves throughout the day
b. to drive transpiration-powered flow in their xylem tissue
c. to help determine whether to open or close their stomata
d. to set their “internal clock,” which influences many metabolic processes
e. to cool their leaves by using light to promote evaporative cooling

Answer 26

e. to cool their leaves by using light to promote evaporative cooling

Question 27

Which of the following is not a function resulting from the action of guard cells?

a. lowering the loss of water upon detecting certain signals from water-stressed roots
b. keeping the leaves at a more positive water potentialrelative to the roots
c. allowing an optimal rate of photosynthesis to occur byletting CO2 enter the leaf
d. permitting cooling of the leaf by the evaporative loss of water
e. allowing water to exit the leaf and so generating tension in the xylem tissue

Answer 27

b. keeping the leaves at a more positive water potentialrelative to the roots

Question 28

If you were grading an exam question about the functions of phloem, which of the following answers would lose points?

a. Pass organic matter from sink to physiological sourcefor storage.
b. Transmit electrical signals between organs of the plant.
c. Carry hormones from one organ to another.
d. Carry various types of RNAs for use in other parts of the plant.
e. Pass information about an ongoing infection to the rest of the plant.

Answer 28

a. Pass organic matter from sink to physiological sourcefor storage.

Question 29

If you wanted to engineer a plant for more efficient capture of light energy, which of the following would be best to alter?

a. Casparian strip effectiveness
b. phyllotaxy
c. mesophyll cell wall thickness
d. xylem cell length
e. phloem plasmodesmata number

Answer 29

b. phyllotaxy

Question 30

If leaf cells have become flaccid, what could you do to reverse that process?

a. Add salt to the soil.
b. Add sugar to the roots.
c. Add water to the leaves.
d. b or c
e. a or b

Answer 30

c. Add water to the leaves.

Question 31

If you genetically transformed a plant to have fewer aquaporins in its root cells and then deprived those cells of water, what would be the effect when you placed the roots in a glass of water?

a. The rehydration of root cells would be slowed.
b. Solute concentrations in root cells would increase.
c. Leaves would wilt.
d. Uptake of salts by roots would be enhanced.

Answer 31

a. The rehydration of root cells would be slowed.

Question 32

If you added a chemical to leaves to stop stomatal opening, what would happen to the xylem?

a. The xylem cells would die.
b. The water in the xylem would stop moving.
c. Phloem sap would leak into the xylem.
d. The xylem would swell.

Answer 32

b. The water in the xylem would stop moving.

Question 33

CAM helps plants cope with _____.

a. low-nutrient soils
b. excessive atmospheric carbon dioxide
c. waterlogged soils
d. very dry habitats

Answer 33

d. very dry habitats

Question 34

If a potato tuber sends sugar to the rest of the plant during spring but receives sugar from the rest of the plant during summer, it moves from being _____.

a. a source to a sink
b. a store of salts to lacking them
c. a below-ground structure to an above-ground structure
d. a vegetative organ to a fruit

Answer 34

a. a source to a sink

Question 35

Phloem sap flows from source to sink because of _____.

a. adhesion
b. positive pressure
c. salt concentrations
d. root pressure
e. cohesion

Answer 35

b. positive pressure

Question 36

Phloem sap flows from source to sink because of _____.

a. adhesion
b. positive pressure
c. salt concentrations
d. root pressure
e. cohesion

Answer 36

b. positive pressure

Question 37

Which of the following is an adaptation that enhances the uptake of water and minerals by roots?

a. mycorrhizae
b. pumping through plasmodesmata
c. active uptake by vessel elements
d. rhythmic contractions by cells in the root cortex

Answer 37

a. mycorrhizae

Question 38

Which structure or compartment is part of the symplast?

a. the interior of a vessel element
b. the interior of a sieve tube
c. the cell wall of a mesophyll cell
d. an extracellular air space

Answer 38

b. the interior of a sieve tube

Question 39

Movement of phloem sap from a source to a sink

a. occurs through the apoplast of sieve-tube elements.
b. depends ultimately on the activity of proton pumps.
c. depends on tension, or negative pressure potential.
d. results mainly from diffusion.

Answer 39

b. depends ultimately on the activity of proton pumps.

Question 40

Photosynthesis ceases when leaves wilt, mainly because

a. the chlorophyll in wilting leaves is degraded.
b. accumulation of CO2 in the leaf inhibits enzymes.
c. stomata close, preventing CO2 from entering th e leaf
d. photolysis, the water-splitting step of photosynthesis, cannot occur when there is a water deficiency.

Answer 40

c. stomata close, preventing CO2 from entering th e leaf

Question 41

What would enhance water uptake by a plant cell?

a. decreasing the water potential (symbol) of the surrounding solution
b. positive pressure on the surrounding solution
c. the loss of solutes from the cell
d. increasing the water potential (symbol) of the cytoplasm

Answer 41

b. positive pressure on the surrounding solution

Question 42

A plant cell with a water potential(S)(symbol) of -0.65 MPa maintains a constant volume when bathed in a solution that has a water potential(s) of -0.30 MPa and is in an open container. The cell has a __.

a. water potential of +0.65 MPa
b. water potential of -0.65 MPa
c. water potential of +0.35 MPa
d. water potential of 0 MPa

Answer 42

c. water potential of +0.35 MPa

Question 43

Compared with a cell with few aquaporin proteins in its membrane, a cell containing many aquaporin proteins will

a. have a faster rate of osmosis.
b. have a lower water potential.
c. have a higher water potential.
d. accumulate water by active transport.

Answer 43

a. have a faster rate of osmosis.

Question 44

Which of the following would tend to increase transpiration?

a. spiny leaves
b. sunken stomata
c. a thicker cuticle
d. higher stomatal density

Answer 44

d. higher stomatal density