Campbell Biology, 10e (Reece)
Chapter 39 Plant Responses to Internal and External Signals
1) The detector of light during de-etiolation (greening) of a tomato plant is (are) _____.
A) carotenoids
B) xanthophylls
C) phytochrome
D) auxin
2) Plant hormones _____.
A) in plant cells naturally exist in very large amounts
B) change their shape in response to stimulus
C) are unable to move from one cell to another
D) affect only cells with the appropriate receptor
3) Which of the following can function in signal transduction in plants ?
I) calcium ions
II) nonrandom mutations
III) receptor proteins
IV) autochrome
V) secondary messengers
A) only I, III, and IV
B) only I, II, and V
C) only I, III, and V
D) only II, III, and V
4) 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
5) Plant hormonal regulation differs from animal hormonal regulation in that _____.
A) there are no dedicated hormone-producing organs in plants as there are in animals
B) all production of hormones is local in plants with little long-distance transport
C) only animal hormone concentrations are developmentally regulated
D) only animal hormones may have either external or internal receptors
6) Which of the following plant growth responses is primarily due to the action of auxins?
A) leaf abscission
B) cell division
C) the detection of photoperiod
D) phototropism
7) Auxins in plants are known to affect which of the following processes?
I) gravitropism of shoots
II) maintenance of seed dormancy
III) phototropism of shoots
IV) inhibition of lateral buds
V) apical dominance
A) only I and II
B) only I, III and V
C) only I, III, IV and V
D) only II, III, IV and V
8) Experiments on the positive phototropic response of plants indicate that _____.
A) light destroys auxin
B) auxin moves down the plant apoplastically
C) auxin is synthesized in the area where the stem bends
D) auxin can move to the shady side of the stem
9) Which of the following statements best summarizes the acid-growth hypothesis in an actively
growing shoot?
A) Auxin stimulates proton pumps in the plasma membrane and tonoplast.
B) Auxin-activated proton pumps lower the pH of the cell wall, which breaks bonds and makes
the walls more flexible.
C) Auxins and gibberellins together act as a lubricant to help stretch cellulose microfibrils.
D) Auxins activate aquaporins that increase turgor pressure in the cells.
10) Which of the following conclusions is supported by the research of both Went and Charles
and Francis Darwin on shoot responses to light?
A) When shoots are exposed to light, a chemical substance migrates toward the light.
B) A chemical substance involved in shoot bending is produced in shoot tips.
C) Once shoot tips have been cut, normal growth cannot be induced.
D) Light stimulates the synthesis of a plant hormone that responds to light.
11) 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) Apply auxin directly to the shoot tip on the side to which you want the tip 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) 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.
12) 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 the tips of the main shoots.
C) Cut off lower branches.
D) Cut off the leaves at the base of most of the branches.
13) As cytokinins are primarily produced in roots, what route would they travel to influence
lateral shoot formation in a recently topped tree?
A) symplastic
B) trachieds/vessels
C) phloem
D) apoplastic
14) Who might be interested in using cytokinins?
A) grocers, to spray on fruit to enhance ripening in the store
B) consumers, to spray on fruit before eating to enhance taste
C) florists, to dip stems in to keep leaves green longer
D) farmers, to spray on fruit after picking to stall ripening
15) If a farmer wanted more loosely packed clusters of grapes, he would most likely spray the
immature bunches with _____.
A) auxin
B) gibberellins
C) cytokinins
D) abscisic acid
16) A researcher found a beautiful plant while traveling in Alaska and collected its seeds. When
she came back to Florida, she soaked some seeds in pure water and some in water with a
hormone. When she put the seeds in soil to grow, only the seeds that had been soaked with the
hormone germinated. The hormone most likely was _____.
A) gibberellin
B) abscisic acid (ABA)
C) auxin
D) ethylene
17) _____ prevents seeds from germinating until conditions are favorable for the growth of the
plant.
A) Ethylene
B) Zeaxanthin
C) Gibberellin
D) Abscisic acid
18) 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 do.
A) auxin
B) gibberellin
C) cytokinin
D) abscisic acid
19) 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) carbon dioxide
B) cytokinins
C) ethylene
D) auxin
20) In the fall, the leaves of some trees change color. This happens because chlorophyll breaks
down and the accessory pigments become visible. What hormone is responsible for this?
A) phototropin
B) abscisic acid
C) cytokinin
D) ethylene
21) Which type of mutant would be most likely to produce a bushier phenotype?
A) auxin overproducer
B) strigolactone overproducer
C) cytokinin underproducer
D) strigolactone underproducer
22) Plant growth regulators _____.
A) only act by altering gene expression
B) often have a multiplicity of effects
C) function independently of other hormones
D) affect the division and elongation, but not the differentiation, of cells
23) 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 thigmotropism
B) negative phototropism
C) negative gravitropism
D) the opposite of circadian rhythms
24) In lettuce seeds, blue light initiates germination. If you measured hormone levels within the
seed, which hormone would be produced upon exposure to blue light?
A) gibberellin
B) ethylene
C) abscisic acid
D) cytokinins
25) Upon exposure to blue light, plants not only begin to grow toward the light, but move their
chloroplasts to the sunny side of each cell. The adaptive advantage of moving chloroplasts to the
sunny side of each cell _____.
A) maximizes light absorption by the chloroplasts for photosynthesis
B) increases production of phototropic hormones
C) maximizes heat absorption by the chloroplasts for cellular respiration
D) increases adenosine triphosphate (ATP) production during the light-independent reactions
26) 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) auxin and phytochrome
B) auxin and Pfr
C) Pfr and phytochrome
D) cytokinins and phototropins
27) Seed packets give a recommended planting depth for the enclosed seeds. The most likely
reason some seeds are to be covered with only -inch of soil is that the _____.
A) seedlings do not have an etiolation response
B) seeds require light to germinate
C) seeds require a higher temperature to germinate
D) seeds are very sensitive to waterlogging
28) Suppose a plant had a photosynthetic pigment that absorbed far-red wavelengths of light. In
which of the following environments could that plant thrive?
A) on the surface of a lake
B) on the forest floor, beneath a canopy of taller plants
C) on the ocean floor, in very deep waters
D) on mountaintops, closer to the Sun
29) The biological clock controlling circadian rhythms must ultimately _____.
A) depend on environmental cues
B) affect gene transcription
C) stabilize on a 24-hour cycle
D) speed up or slow down with increasing or decreasing temperature
30) Many plants flower in response to day-length cues. Which of the following statements best
summarizes this phenomenon?
A) As a rule, short-day plants flower in the summer.
B) As a rule, long-day plants flower in the spring or fall.
C) Long-day plants flower in response to long days, not short nights.
D) Flowering in short-day and long-day plants is controlled by phytochrome.
31) 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 more predictable than air temperature changes
B) predict moisture availability
C) are modified by soil temperature changes
D) can reset the biological clock
32) A gardener in Canada wants to surprise his mother on her birthday and make her favorite
hibiscus bush flower in May instead of at the end of June. The bush is growing in the
greenhouse. Which of the following might make the hibiscus bush flower early?
A) grafting leaves of a hibiscus that was exposed to long night
B) grafting leaves of a hibiscus that was exposed to short night
C) exposing flower buds of the hibiscus bush to long nights
D) exposing flower buds of the hibiscus bush to short nights
33) Which of the following can be sensed by plants?
I) gravity
II) pathogens
III) wind
IV) light
A) only I and III
B) only I, II, and IV
C) only II, III, and IV
D) I, II, III, and IV
34) You have discovered a previously unidentified plant, and you cultivate it in your lab. You
notice that its flowers close when people are talking, yet are open when the lab is relatively quiet.
You suspect that this plant may have the ability to hear! Which of the following hypotheses is
(are) the most reasonable to explain this phenomenon?
I) There is a cell-surface protein on the epidermal cells that becomes phosphorylated in
response to vibration by sound waves.
II) There are tiny hairs on epidermal cells that bend in response to the vibration of sound waves,
triggering an action potential in epidermal cells.
III) There is a cell-surface receptor on root cells that becomes phosphorylated when the soil
vibrates in response to sound waves.
A) only I
B) only II
C) only III
D) I, II, and III
35) Shoots that grow vertically toward the sun can be characterized as _____.
A) positive for phototropism and negative for gravitropism
B) neutral for phototropism and positive for gravitropism
C) negative for phototropism and positive for gravitropism
D) positive for phototropism and neutral for gravitropism
36) Suppose you laid a seedling on its side so that the root was parallel to the ground as shown in
the figure above. Several hours after the change in position, where in the root cells (position A,
B, or C in the figure above) would you find the amyloplasts?
A) A
B) B
C) C
37) The rapid leaf movements resulting from a response to touch (thigmotropism) primarily
involve _____.
A) potassium channels
B) nervous tissue
C) aquaporins
D) stress proteins
38) In extremely cold regions, woody species may survive freezing temperatures by _____.
A) emptying water from the vacuoles to prevent freezing
B) decreasing the numbers of phospholipids in cell membranes
C) decreasing the fluidity of all cellular membranes
D) increasing cytoplasmic levels of specific solute concentrations, such as sugars
39) 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) the production of heat-stable carbohydrates
B) increased production of heat-shock proteins
C) the opening of stomata to increase evaporational heat loss
D) protoplast fusion experiments with xerophytic plants
40) 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) minimize water loss by evaporation from the cut surface
B) improve the appearance of the cut surface
C) stimulate growth of the cork cambium to “heal” the wound
D) block entry of pathogens through the wound
41) 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) avirulence response
B) hypersensitive response
C) resistance response
D) virulence response
42) Generalized defense responses in organs distant from the infection site are called _____.
A) hyperactive responses
B) systemic acquired resistance
C) pleiotropy
D) hyperplasia
43) A certain bacterium infects a plant’s upper leaves. A few days later, bacteria of the same
species attempt to infect the same plant’s roots but are unsuccessful. What process is responsible
for the plant’s ability to prevent this infection?
A) antivirulence response
B) pathogenesis resistance
C) systemic acquired resistance
D) sequential immunity
44) A particular species of virus carries a gene for salicylate hydroxylase, an enzyme that breaks
down salicylic acid. Will this virus be more or less virulent to plants than other viruses?
A) more
B) less
C) This will not make the virus more or less virulent.
45) Which event during the evolution of land plants favored the synthesis of secondary
compounds?
A) the greenhouse effect throughout the Devonian period
B) the reverse-greenhouse effect during the Carboniferous period
C) the association of the roots of land plants and fungi
D) the rise of herbivory
46) The major function of the medicinal compounds in plants is to _____.
A) attract pollinators for seed dispersal
B) attract insects and birds to spread seeds and fruits
C) defend the plant against herbivores
D) defend the plant against microbes
47) For a plant to initiate chemical responses to herbivory, before it is directly affected by
herbivores, _____.
A) a plant must have already flowered at least once
B) volatile “signal” compounds must be perceived
C) gene-for-gene intraspecific recognition must occur
D) phytoalexins must be released
Use the following information to answer the question(s) below.
Some plants have continually produced secondary defense compounds. Other plants are induced
to form secondary defense compounds when they are injured. Corn seedling leaves that are
chewed on by the caterpillars of a type of cutworm moth emit immediate volatile chemicals
(LOX products), and after six hours large amounts of terpenoid compounds are released into the
air. The terpenoids are released not only from the leaf being chewed, but from all leaves of the
plant. The terpenoid compounds attract a parasitoid wasp female that lays her eggs on the
caterpillar. When the wasp larvae hatch, they eat and kill the moth caterpillar. (T.C.J. Turlings, J.
H. Loughrin, P. J. McCall, U. S. R. Rose, W. J. Lewis, and J. H. Tumlinson. 1995. How
caterpillar-damaged plants protect themselves by attracting parasitic wasps. Proceedings of the
National Academy of Sciences 92:4169-74.)
48) Refer to the paragraph on how caterpillar-damaged plants protect themselves by attracting
parasitic wasps. What can you conclude based only on the information in the preceding
paragraph?
A) The attracting terpenoid compounds are always present in the corn seedling.
B) Physical injury by the caterpillar mouthparts results in the immediate release of terpenoids.
C) Chemical signals from the caterpillar saliva attract the parasitic wasp.
D) The parasitoid wasp is attracted by compounds produced by an injured corn plant.
49) Refer to the paragraph on how caterpillar-damaged plants protect themselves by attracting
parasitic wasps. To test the hypothesis that caterpillar saliva and a wound are both necessary to
attract the parasitoid wasps you would need to include which of the following in your
experiment?
I) Slash the corn leaves with a razor blade.
II) Put caterpillar saliva on a leaf wound.
III) Put caterpillar saliva on an intact leaf.
A) only I
B) only II
C) only III
D) I, II, and III
50) 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) Cover the growing tip of the grass seedling with black paper.
B) Supply the seedlings with very dim light. fired light does not induce a bend)
C) Cover the portion of the seedling below the tip with a black shield.
D) Supply the seedling with nutrient-rich fertilizer solution.
51) 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 long-day (short-night) plants. Which
of the following has the best chance of creating iris blooms in winter?
A) Artificially increase the period of darkness in the greenhouse.
B) Increase the temperature to more closely follow summer temperatures.
C) Alternate four hours of darkness with four hours of light repeatedly over each 24-hour period.
D) Interrupt the long winter nights with a brief period of light.
52) 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 was too short to attract insects for pollination.
B) The plant could not adjust to directional light, which reduced photosynthetic activity and
therefore energy available for reproduction.
C) Because the plant grew much taller and straighter, resources that could be used for
reproduction were used for growth.
D) The loss of a phototropic response meant that the plant’s seeds could not germinate so
reproduction would be unsuccessful.