Chapter 39 Questions

Question 1

Plant hormones produce their effects by ___.
I. altering the expression of genes
II. modifying the permeability of the plasma membrane
III. modifying the structure of the nuclear envelope membrane
a. only I
b. only II
c. only III
d. only I and II

Answer 1

d. only I and II

Question 2

Plant hormonal regulation differs from animal hormonal regulation in that ___.

a. only animal hormone concentrations are developmentally regulated
b. all production of hormones is local in plants with little long-distance transport
c. only animal hormones may have either external or internal receptors
d. there are no dedicated hormone-producing organs in plants as there are in animals

Answer 2

d. there are no dedicated hormone-producing organs in plants as there are in animals

Question 3

Arrange the following steps that occur during drought tolerance in plants in a correct sequence.
I. hormone ABA accumulation in the leaves
II. causes stomata to close
III. reduction in transpiration
IV. preventing further water loss
a. I, III, II, and IV
b.  I, II, III, and IV
c. II, I, III, and IV
d. III, I, II, and IV

Answer 3

b. I, II, III, and IV

Question 4

An eccentric millionaire botanist has offered a $25,000 scholarship to anyone who can successfully get a plant to grow through a vertical maze in complete darkness. The maze is not in a box; the maze is simply drawn on the wall, and the contestants must get their plant to grow in a pattern that matches the path through the maze. You need the money and feel confident that you can accomplish this task. Which of the following techniques will help you succeed?

a. Plant the roots in two different pots, and apply auxin to the root bucket that is on the same side as the direction you want the plant to bend.
b. Apply auxin directly to the part of the stem just below the tip opposite from the direction you want the stem to bend.
c. Inject compounds that block auxin receptors into the part of the stem opposite from the direction you want the stem to bend.
d. Apply auxin directly to the shoot tip on the side to which you want the tip to bend.

Answer 4

b. Apply auxin directly to the part of the stem just below the tip opposite from the direction you want the stem to bend.

Question 5

You have a small tree in your yard that is the height that you want it, but does not have as many branches as you want. How can you prune it to trigger it to increase the number of branches?

a. Cut off the leaves at the ends of several branches.
b. Cut off lower branches.
c. Cut off the tips of the main shoots.
d. Cut off the leaves at the base of most of the branches.

Answer 5

c. Cut off the tips of the main shoots.

Question 6

A population of plants experiences several years of severe drought. Much of the population dies due to lack of water, but a few individuals survive. You set out to discover the physiological basis for their adaptation to such an extreme environmental change. You hypothesize that the survivors have the ability to synthesize higher levels of ___ than their siblings.

a. auxin
b. cytokinin
c. gibberellin
d. abscisic acid

Answer 6

d. abscisic acid

Question 7

If you were shipping green bananas to a supermarket thousands of miles away, which of the following chemicals would you want to eliminate from the plants’ environment?

a. auxin
b. carbon dioxide
c. cytokinins
d. ethylene

Answer 7

d. ethylene

Question 8

Which type of mutant would be most likely to produce a bushier phenotype?

a. auxin overproducer
b. cytokinin underproducer
c. strigolactone overproducer
d. strigolactone underproducer

Answer 8

d. strigolactone underproducer

Question 9

Vines in tropical rain forests must grow toward large trees before being able to grow toward the sun. To reach a large tree, the most useful kind of growth movement for a tropical vine presumably would be ___.

a. negative phototropism
b. negative thigmotropism
c. the opposite of circadian rhythms
d. negative gravitropism

Answer 9

a. negative phototropism

Question 10

Upon exposure to blue light, plants not only begin to grow toward the light, the move their chloroplasts to the sunny side of each cell. The adaptive advantage of moving chloroplasts to the sunny side of each cell ___.

a. increases production of phototropic hormones
b. maximizes heat absorption by the chloroplasts for cellular respiration
c. maximizes light absorption by the chloroplasts for photosynthesis
d. increases adenosine triphosphate (ATP) production during the light-independent reactions

Answer 10

c. maximizes light absorption by the chloroplasts for photosynthesis

Question 11

Mammalian eyes sense light because the photoreceptor cells have molecules called opsins, which change structure when exposed to light. Which of the following plant molecules would be analogous to mammalian opsins in their light-sensing ability?

a. cytokinins and phototropins
b. Pfr and phytochrome
c. auxin and phytochrome
d. auxin and Pfr

Answer 11

b. Pfr and phytochrome

Question 12

Seed packets give a recommended planting depth for the enclosed seeds. The most likely reason some seeds are to be covered with only 1/4 inch of soil is that the ___.

a. seeds are very sensitive to waterlogging
b. seeds require a higher temperature to germinate
c. seeds require light to germinate
d. seedlings do not have an etiolation response

Answer 12

c. seeds require light to germinate

Question 13

Suppose a plant had photosynthetic pigment that absorbed far-red wavelengths of light. In which of the following environments could that plant thrive?

a. on the ocean floor, in very deep waters
b. on the surface of a lake
c. on the forest floor, beneath a canopy of taller plants
d. on mountaintops, closer to the Sun

Answer 13

c. on the forest floor, beneath a canopy of taller plants

Question 14

Plants often use changes in day length (photoperiod) to trigger events such as dormancy and flowering. It is logical that plants have evolved this mechanism because photoperiod changes ____.

a. are modified by soil temperature changes
b. can reset the biological clock
c. predict moisture availability
d. are more predictable than air temperature changes

Answer 14

d. are more predictable than air temperature changes

Question 15

Most scientists agree that global warming is underway; thus it is important to know how plants respond to heat stress. Which of the following would be a useful line of inquiry to try and improve plant response and survival to heat stress?

a. protoplast fusion experiments with xerophytic plants
b. increased production of heat-shock proteins
c. the opening of stomata to increase evaporational heat loss
d. the production of heat-stable carbohydrates

Answer 15

b. increased production of heat-shock proteins

Question 16

When an arborist prunes a limb off a valuable tree, he or she may paint the cut surface. The primary purpose of the paint is to ___.

a. stimulate growth of the cork cambium to “heal” the wound
b. improve the appearance of the cut surface
c. block entry of pathogens through the wound
d. minimize water loss by evaporation from the cut surface

Answer 16

c. block entry of pathogens through the wound

Question 17

You are out working in your garden, and you notice that one of your favorite flowering plants has black, dead spots on the leaves. You immediately suspect that the plant has been invaded by a pathogen and has initiated a(n) ___.

a. virulence response
b. avirulence response
c. hypersensitive response
d. resistance response

Answer 17

c. hypersensitive response

Question 18

You may have observed plants rotate towards a light source, thereby increasing the plant’s ability to intercept light energy and increase photosynthesis. You, however, are given the task of preventing grass seedlings from rotating toward the light. Using your knowledge of phototropism, which of the following experimental procedures would you use to complete your task?

a. Supply the seedlings with very dim light (red light does not induce a bend).
b. Cover the portion of the seedling below the tip with a black shield.
c. Supply the seedling with nutrient-rich fertilizer solution.
d. Cover the growing tip fo the grass seedling with black paper.

Answer 18

d. Cover the growing tip fo the grass seedling with black paper.

Question 19

A plant scientist was hired by a greenhouse operator to devise a way to force iris plants to bloom in the short days of winter. Iris normally blooms as a long-day (short-night) plant. Which of the following has the best chance of creating iris blooms in winter?

a. Increase the temperature to more closely follow summer temperatures.
b. Alternate four hours of darkness with four hours of light repeatedly over each 24-hour period.
c. Artificially increase the period of darkness in the greenhouse.
d. Interrupt the long winter nights with a brief period of light.

Answer 19

d. Interrupt the long winter nights with a brief period of light.

Question 20

An individual plant was discovered that could not grow towards light. After some research, it was determined that the reason was a defective gene that did not allow for the level of cell elongation necessary for a phototropic response. This mutation greatly reduces the fitness of the individual plant. Which reason best describes the reason for the loss of fitness?

a. The plant could not adjust to directional light, which reduced photosynthetic activity and therefore energy available for reproduction.
b. The loss of a phototropic response meant that the plant’s seeds could not germinate, so reproduction would be unsuccessful.
c. The plant was too short to attract insects for pollination.
d. Because the plant grew much taller and straighter, resources that could be used for reproduction were used for growth.

Answer 20

a. The plant could not adjust to directional light, which reduced photosynthetic activity and therefore energy available for reproduction.

Question 21

The hormone that helps plants respond to drought is

a. auxin.
b. abscisic acid.
c. cytokinin.
d. ethylene.

Answer 21

b. abscisic acid.

Question 22

Auxin enhances cell elongation in all of these ways except

a. increased uptake of solutes.
b. gene activation.
c. acid-induced denaturation of cell wall proteins.
d. cell wall loosening.

Answer 22

c. acid-induced denaturation of cell wall proteins.

Question 23

Charles and Francis Darwin discovered that

a. auxin is responsible for phototropic curvature.
b. red light is most effective in shoot phototropism.
c. light destroys auxin.
d. light is perceived by the tips of coleoptiles.

Answer 23

d. light is perceived by the tips of coleoptiles.

Question 24

How may a plant respond to severe heat stress?

a. by reorienting leaves to increase evaporative cooling
b. by creating air tubes for ventilation
c. by producing heat-shock proteins, which may protect the plant’s proteins from denaturing
d. by increasing the proportion of unsaturated fatty acids in cell membranes, reducing their fluidity

Answer 24

c. by producing heat-shock proteins, which may protect the plant’s proteins from denaturing

Question 25

The signaling molecule for flowering might be released earlier than usual in a long-day plant exposed to flashes of

a. far-red light during the night.
b. red light during the night.
c. red light followed by far-red light during the night.
d. far-red light during the day.

Answer 25

b. red light during the night.

Question 26

If a long-day plant has a critical night length of 9 hours, which 24-hour cycle would prevent flowering?

a. 16 hours light/8 hours dark
b. 14 hours light/10 hours dark
c. 4 hours light/8 hours dark/4 hours light/8 hours dark
d. 8 hours light/8 hours dark/light flash/8 hours dark

Answer 26

b. 14 hours light/10 hours dark

Question 27

A plant mutant that shows normal gravitropic bending but does not store starch in its plastids would require a reevaluation of the role of in gravitropism.

a. auxin
b. calcium
c. statoliths
d. differential growth

Answer 27

c. statoliths

Question 28

According to the acid growth hypothesis, what role does acid play in cell growth?

a. loosening the cell wall
b. activating gene expression
c. denaturing proteins
d. a and c
e. a, b, and c

Answer 28

a. loosening the cell wall

Question 29

Which is most directly involved in causing the leaves of deciduous trees to fall in autumn?

a. cytokinins
b. gibberellins
c. abscisic acid
d. ethylene
e. brassinosteroids

Answer 29

d. ethylene

Question 30

Circadian rhythms, seasonal rhythms, and seedling germination are most strongly influenced by which colors of light absorbed by phytochrome?

a. violet light and ultraviolet light
b. infrared radiation and red light
c. red light and far-red light
d. blue light and red light
e. geomagnetism and cosmic radiation

Answer 30

c. red light and far-red light

Question 31

The best way to induce a long-day plant to flower when nights are too long is to interrupt the plant’s

a. days with a few minutes of complete darkness during its exposure to light.
b. nights with a few minutes of exposure to blue light.
c. nights with a few minutes of exposure to far-red light.
d. nights with a few minutes of exposure to red light.
e. nights with a few minutes of exposure to any color of light.

Answer 31

d. nights with a few minutes of exposure to red light.

Question 32

To sense gravity in their roots, plants use the distribution of what organelle? What type of gravitropism would these roots display?

a. otoliths; positive gravitropism
b. statoliths; positive gravitropism
c. statoliths; negative gravitropism
d. statocysts; negative gravitropism
e. statocysts; positive gravitropism

Answer 32

b. statoliths; positive gravitropism

Question 33

In response to temperature extremes, plants may synthesize either heat-shock proteins or antifreeze proteins. Which dangers, respectively, do these two proteins protect against?

a. protein denaturation, ice crystal formation
b. wilting, inability to synthesize hormones
c. permanent closure of stomata, evapotranspiration
d. leaf abscission, protein denaturation
e. evapotranspiration, inability to perform motor activities

Answer 33

a. protein denaturation, ice crystal formation

Question 34

Plant cells can do all of the following in response to attack by a pathogen except

a. kill themselves.
b. synthesize chemicals that inhibit the pathogen.
c. limit the spread of the pathogen to other cells.
d. secrete chemicals that signal the presence of pathogens to other parts of the plant.
e. create antibodies against specific items found in the pathogen.

Answer 34

e. create antibodies against specific items found in the pathogen.

Question 35

The leaves at the top of a tree’s canopy are exposed to direct sunlight during the day, and their phytochromes will occur in a high _____ ratio. Meanwhile, the leaves of the same tree at the bottom of the canopy are highly shaded during the day and will likely have a higher proportion of the _____ form of phytochrome present due to exposure to a higher proportion of _____ light.

a. Pfr/Pr; Pr; red
b. Pfr/Pr; Pfr; far-red
c. Pr/Pfr; Pr; far-red
d. Pfr/Pr; Pr; far-red
e. Pfr/Pr; Pfr; red

Answer 35

d. Pfr/Pr; Pr; far-red

Question 36

When a plant’s leaves lack sufficient water, what action will the plant take to attempt to restore their water potential?

a. Its leaves will create more cytokinins to help them retain items needed to avoid senescence.
b. It will spread abscisic acid in its leaves to help induce stomatal pore closure.
c. It will promote root elongation by moving more auxin to the root-elongating region.
d. It will emit ethylene so that leaf senescence is promoted.
e. It will produce more florigen in its leaf tissues.

Answer 36

b. It will spread abscisic acid in its leaves to help induce stomatal pore closure.

Question 37

The systemic acquired resistance seen in vascular plants lasts for several days. If this system was kept always on, then one result might be

a. the accumulation of methyl salicylic acid in the roots of the plant.
b. higher rates of infection by other types of pathogens.
c. the spread of more pathogenic effectors into the plant tissues.
d. reduced growth rate of the plant due to the metabolic costs of deploying this system of resistance.
e. the production of more gibberellins to promote plant stem elongation.

Answer 37

d. reduced growth rate of the plant due to the metabolic costs of deploying this system of resistance.

Question 38

What will happen to seeds exposed to the following colors of light for 1 minute each, in the order given: red, far-red, far-red, red, far-red, red, red, far-red, red?

a. They will deepen their dormancy.
b. They will kill themselves via apoptosis.
c. They will germinate.
d. They will require a cold treatment.
e. They will produce ethylene.

Answer 38

c. They will germinate.

Question 39

Your friend puts a chemical on a banana and tells you to observe it for two days. The banana, which had been green, becomes yellow and soft. The chemical used by your friend must be

a. cytokinin.
b. ethylene.
c. gibberellin.
d. auxin.
e. brassinosteroid.

Answer 39

b. ethylene.

Question 40

You observe workers in a greenhouse slicing leaves from African violet plants, dipping the cut ends in a white powder, and placing the cut ends into potting mix. The white powder probably contains

a. cytokinin.
b. ethylene.
c. gibberellin.
d. auxin.
e. brassinosteroid.

Answer 40

d. auxin.

Question 41

If you needed to buy lightbulbs for an experiment on plant development, which colors of bulbs should you choose?

a. hypersensitive response
b. systemic acquired resistance
c. latex production
d. heat-shock proteins
e. none of the above

Answer 41

a. hypersensitive response