Deck 39: Plant Responses to Internal and External Signals

Question 1

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.

Answer 1

B

Question 2

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

Answer 2

C

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, II, III, and IV
B) I, III, II, and IV
C) II, I, III, and IV
D) III, I, II, and IV

Answer 3

A

Question 4

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

Question 5

What are the primary sites of ethylene production in high concentrations in plants?

A) shoot apical meristem and young leaves
B) roots
C) seeds
D) ripening fruits

Question 6

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

Question 7

Apical dominance in plants is under the control of ________.

A) sugar
B) various plant hormones
C) cell division
D) sugar and various plant hormones

Question 8

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.

Question 9

The detector of light during de-etiolation (greening) of a tomato plant is (are) ________.

A) carotenoids
B) xanthophylls
C) phytochrome
D) auxin

Question 10

Which of the following mechanisms is the correct sequence of events that takes place during the plant responses to internal and external signals?

A) transduction, reception, and response
B) reception and transduction
C) reception, transduction, and response
D) reception and response

Question 11

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

Question 12

Which one of the following hormones regulates cell division in plants?

A) auxin (IAA)
B) ethylene
C) gibberellins
D) cytokinins

Question 13

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.

Question 14

What are the primary sites of auxin (IAA) production in plants?

A) shoot apical meristem and young leaves
B) roots
C) seeds
D) ripening fruits

Question 15

Which of the following mechanisms is in the correct sequence of steps (I-IV as listed below) that takes place during the formation of de-etiolation (greening) response proteins in plants?
I)Detection of light signal
II)Activation of phytochrome
III)Activation of specific protein kinase1
IV)Formation of de-etiolation response protein

A) I, III, II, and IV
B) I, II, III, and IV
C) II, I, III, and IV
D) III, I, II, and IV

Question 16

Generally, each hormone has multiple functions in plants depending on ________.
I)site of action
II)its concentration
III)developmental stage
IV)age

A) I, II, III, and IV
B) I, II, and III
C) I and II
D) II

Question 17

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

Question 18

Which one of the following hormones stimulates stem elongation and pollen tube growth?

A) auxin (IAA)
B) ethylene
C) gibberellins
D) cytokinins

Question 19

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

Question 20

Which of the following conclusions is supported by the research of both Peter Boysen-Jensen 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.

Question 21

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

Question 22

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

Question 23

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

Question 24

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 nights
B) grafting leaves of a hibiscus that was exposed to short nights
C) exposing flower buds of the hibiscus bush to long nights
D) exposing flower buds of the hibiscus bush to short nights

Question 25

Which of the following environmental factors 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

Question 26

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

Question 27

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

Question 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

Question 29

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

Question 30

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

Question 31

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) 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

Question 32

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

Question 33

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

Question 34

Phytochrome plays a critical role in seed germination. Which of the colors maximizes the seed germination?

A) red
B) blue
C) violet
D) orange

Question 35

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

Question 36

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

Question 37

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) tracheids/vessels
C) phloem
D) apoplastic

Question 38

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.

Question 39

Which of the colors of visible light induces curvature in coleoptile most effectively?

A) red
B) blue
C) violet
D) orange

Question 40

________ prevents seeds from germinating until conditions are favorable for the growth of the plant.

A) Ethylene
B) Zeaxanthin
C) Gibberellin
D) Abscisic acid

Question 41

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) 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.

Question 42

Use the figure to answer the following question.

Suppose you laid a seedling on its side so that the root was parallel to the ground as shown in the figure. Several hours after the change in position, where in the root cells, position A, B, or C in the figure, would you find the amyloplasts?

A) A
B) B
C) C
D) A and C

Question 43

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

Question 44

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

Question 45

The rapid leaf movements resulting from a response to touch (thigmotropism) primarily involve ________.

A) potassium channels
B) nervous tissue
C) aquaporins
D) stress proteins

Question 46

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.

Question 47

The hormone that helps plants respond to drought is

A) auxin.
B) abscisic acid.
C) cytokinin.
D) ethylene.

Question 48

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

Question 49

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

Question 50

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.

Question 51

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.

Question 52

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

Question 53

Generalized defense responses in organs distant from the infection site are called ________.

A) hyperactive responses
B) systemic acquired resistance
C) pleiotropy
D) hyperplasia

Question 54

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 (red 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.

Question 55

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

Question 56

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

Question 57

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.

Question 58

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 virulent
B) less virulent
C) same virulent
D) faster virulent

Question 59

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

Question 60

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

Question 61

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