Deck 38: Plant Developmental Responses to External and Internal Signals

Question 1

The herbicides (weed killers) 2,4-D and 2,4,5-T are examples of synthetic:

A) abscisic acid.
B) auxins.
C) cytokinins.
D) ethylene.
E) gibberellins.

Answer 1

B

Question 2

You expose a plant to a light that shines on the right side of a plant. Which statement best describes why the plant grows toward the light?

A) Light destroys auxin, and thus the shaded side grows faster.
B) Auxin moves from the shaded side to the lighted side where it stimulates growth.
C) Auxin moves from the lighted side to the shaded side where it stimulates growth.
D) Light destroys auxin and thus the lighted side grows faster.
E) Auxin moves from the shaded side to the lighted side where it inhibits growth.

Answer 2

C

Question 3

You want to obtain the strongest phototropic response from a shoot. Which wavelength of light should you use?

A) less than 500 nm
B) 660 nm
C) 730 nm
D) 800 nm
E) more than 800 nm

Answer 3

A

Question 4

What hormone promotes apical dominance in plants?

A) abscisic acid
B) auxin
C) cytokinin
D) ethylene
E) gibberellin

Question 5

Which of the following would be the most likely consequence of removing the apical meristem from a plant?

A) The plant dies.
B) The plant remains alive but will not grow again.
C) The growth of axillary buds is inhibited.
D) The axillary buds die.
E) Some axillary buds grow into branches.

Question 6

Changing day length, as well as variations in precipitation and temperature, are environmental cues that exert an important influence on:

A) the kinds of genes a plant has.
B) the number of mutations that genes undergo.
C) whether a plant is an annual, biennial, or perennial.
D) which genes will be expressed in a plant.
E) whether a plant reproduces sexually or asexually.

Question 7

When a plant responds to external stimuli, such as light, gravity, or touch by directional growth, these responses are referred to as:

A) turgor movements.
B) sleep movements.
C) nastic movements.
D) circadian rhythms.
E) tropisms.

Question 8

The photoreceptor that absorbs blue light and triggers a phototropic response is:

A) phototropin.
B) phytochrome.
C) jasmonate.
D) systemin.
E) zeatin.

Question 9

____ is a synthetic auxin that stimulates root development on stem cuttings and is used extensively in asexual propagation.

A) Indoleacetic acid
B) Indolebutyric acid
C) Naphthalene acetic acid
D) 2,4-D
E) 2,4,5-T

Question 10

The application of ____ substitutes for low temperature or light requirements for biennial germination.

A) indoleacetic acid
B) indolebutyric acid
C) naphthaleneacetic acid
D) gibberellins
E) ethephon

Question 11

The site of gravity reception in roots is the:

A) root apical meristem.
B) periderm.
C) root epidermis.
D) root cap.
E) root hair.

Question 12

In barley seed germination, the ____ releases gibberellin, which triggers the synthesis of ____ in the ____.

A) seed coat; α -amylase; embryo
B) endosperm; cellulase; embryo
C) embryo; α -amylase; endosperm
D) embryo; cellulase; seed coat
E) endosperm; β -amylase; embryo

Question 13

Auxin sprayed on tomato flowers stimulates the ____ to develop without the formation of ____.

A) roots; root hairs
B) fruit; ovaries
C) seeds; ovaries
D) ovary; seeds
E) seeds; fruits

Question 14

Which hormone promotes cell division and delays senescence in plants?

A) abscisic acid
B) auxin
C) cytokinin
D) ethylene
E) gibberellin

Question 15

____ is growth in response to a mechanical stimulus, such as contact with a solid object.

A) Heliotropism
B) Phototropism
C) Gravitropism
D) Thigmotropism
E) Geotropic bending

Question 16

A seedling growing toward the source of light is an example of:

A) shade avoidance.
B) a positive hypersensitive response.
C) a negative hypersensitive response.
D) a positive phototropic response.
E) a negative phototropic response.

Question 17

Which hormone promotes stem elongation and was first discovered while studying the growth of extremely tall and spindly rice plants?

A) abscisic acid
B) auxin
C) cytokinin
D) ethylene
E) gibberellin

Question 18

You would like to develop an herbicide that is structurally most similar to cytokinin. Which of the following molecules would you use as starting material?

A) adenine
B) glucose
C) naphthaleneacetic acid
D) α -amylase
E) a steroid

Question 19

When a root is placed on its side, what happens to the amyloplasts in the root cap cells?

A) They move away from the direction of gravity.
B) They settle in the direction of gravity
C) They are digested by amylase.
D) They move into the root apical meristem.
E) They move into a root hair.

Question 20

____ stimulates rapid elongation of a floral stalk in many plant species.

A) Abscisic acid
B) Gibberellin
C) Cytokinin
D) Ethylene
E) Auxin

Question 21

Which statement concerning the auxin F-box protein is false ?

A) It is located in the nucleus.
B) It is a type of receptor.
C) It is involved in catalyzing the addition of ubiquitin tags.
D) Plants have about 700 of these.
E) An example is the transport inhibitor response 1 protein.

Question 22

The movement of auxin downward from its site of production is referred to as:

A) gravitropism.
B) apical dominance.
C) nonpolar transport.
D) polar transport.
E) turgor movement.

Question 23

The "stress hormone" involved in stomatal closure during water stress is:

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

Question 24

Unripe green fruits ripen quickly in supermarkets or commercial storage facilities after exposure to:

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

Question 25

Which hormone promotes cell elongation by changing plant cell walls so they can expand due to the force of turgor pressure?

A) abscisic acid
B) auxin
C) cytokinin
D) ethylene
E) gibberellin

Question 26

Brassinosteroids differ from other plant hormones in that they are:

A) peptides.
B) steroids.
C) derivatives of adenine.
D) derivatives of aspirin.
E) derivatives of prostaglandins.

Question 27

Figure 38-1 One conclusion that can be drawn from the accompanying figure is that a low ratio of auxin to cytokinin:

A) stimulates root development.
B) stimulates shoot development.
C) results in undifferentiated growth.
D) stimulates the formation of an entire plant.
E) results in no growth.

Question 28

In the mechanism of action for auxin, after auxin binds with its receptor, which of the following happens next?

A) Proteins are targeted for destruction.
B) Genes are activated.
C) Ubiquitin attaches to repressor proteins.
D) Transcription occurs.
E) The cell wall loosens.

Question 29

What hypothetical hormone promotes flowering but has never been successfully isolated?

A) florigen
B) ubiquitin
C) jasmonic acid
D) brassinosteroids
E) methyl salicylate

Question 30

Which of the following would be characteristic of a plant exhibiting shade avoidance?

A) stem elongation
B) more leaves
C) higher quantity of storage products
D) more reproductive tissue
E) more branches

Question 31

You place a coleoptile in unidirectional light and then immediately cover the tip. Which of the following will happen?

A) The coleoptile would bend toward the light.
B) The coleoptile would not bend.
C) The coleoptile would bend away from the light.
D) The coleoptile would die.
E) The coleoptile would grow in a spiral pattern.

Question 32

Figure 38-1 Based on the data in the accompanying figure, the condition that results in root development is:

A) a high ratio of auxin to cytokinin.
B) a low ratio of auxin to cytokinin.
C) a relatively equal proportion of auxin to cytokinin.
D) cytokinin levels of at least 0.2 mg/L.
E) auxin concentrations of 0.5 mg/L.

Question 33

The purification and elucidation of the primary auxin's chemical structure were accomplished by:

A) Charles Darwin.
B) Francis Darwin.
C) Frits Went.
D) Kenneth Thimann.
E) F. Skoog.

Question 34

Which hormone stimulates both leaf abscission and fruit ripening?

A) abscisic acid
B) auxin
C) cytokinin
D) ethylene
E) gibberellin

Question 35

You plant two gardens, one in the sun and one in the shade. The plants grown in the shade will most likely be ____ because neighboring leaves absorb more ____.

A) shorter; far-red light than red light
B) shorter; red light than far-red light
C) taller; red light than far-red light
D) taller; far-red light than red light
E) shorter; cryptochrome than phytochrome

Question 36

The most common and physiologically important auxin is:

A) indoleacetic acid.
B) indolebutyric acid.
C) naphthaleneacetic acid.
D) 2,4-D.
E) 2,4,5-T.

Question 37

Which of the following statements about plant hormones is false ?

A) They are organic compounds that act as a highly specific chemical signal.
B) They are effective in extremely small amounts.
C) They elicit many different responses.
D) They may stimulate a response at one concentration and inhibit that same response at a different concentration.
E) They currently can be categorized into seven major classes.

Question 38

A plant growth response to mechanical stress, such as rain and contact with passing animals, is known as:

A) phototropism.
B) gravitropism.
C) thigmomorphogensis.
D) a circadian rhythm.
E) thigmotropism.

Question 39

____ is believed to be produced in the leaves and transported to the phloem in the shoot apical meristem.

A) Jasmonic acid
B) Florigen
C) Brassinosteroid
D) Abscisic acid
E) Ethylene

Question 40

____ used tiny blocks of agar to show that auxin is made in the tip of coleoptiles and still capable of influencing bending of the coleoptile.

A) Charles Darwin
B) Francis Darwin
C) Frits Went
D) Kenneth Thimann
E) Frits Skoog

Question 41

You shine light having a wavelength of 660 nm on a plant. Which of the following will most likely happen next?

A) Pfr is stored for later use.
B) Pr is synthesized.
C) Pr is converted to Pfr.
D) Pfr is converted to Pr.
E) Pr is degraded.

Question 42

Figure 38-2 The plant in Row B of the accompanying figure demonstrates a photoperiodic response characteristic of:

A) short-day plants.
B) day-neutral plants.
C) long-day plants.
D) long-night plants.
E) intermediate-day plants.

Question 43

An example of a long-day plant is:

A) poinsettia.
B) florist's chrysanthemum.
C) sunflower.
D) black-eyed Susan.
E) sugarcane.

Question 44

Plants compete for light, a response known as ____, in which plants tend to grow taller when closely surrounded by other plants.

A) epinasty
B) phototropism
C) shade avoidance
D) shade tolerance
E) thigmotropism

Question 45

Which statement concerning phytochrome-induced responses is false ?

A) All responses are very rapid and short-term.
B) Red light causes potassium channels to open.
C) The absorption of light by one part of the phytochrome molecule triggers a conformational change in another part.
D) Phytochrome activates transcription of the gene for a subunit of rubisco.
E) Far-red light causes potassium channels to close.

Question 46

Which statement about the internal biological clock is false ?

A) It is known as a circadian rhythm.
B) It relates to the opening and closing of stomata.
C) It includes the sleep movements observed in some plants, such as beans.
D) It may involve both phytochrome and cryptochrome.
E) It disappears totally if it is not reset by the rising and setting sun.

Question 47

Pr is located in the ____, and after it absorbs red light, the resulting Pfr moves to the ____.

A) endoplasmic reticulum; plasma membrane
B) cytoplasm; nucleus
C) plasma membrane; cytoplasm
D) cytoplasm; plasma membrane
E) nucleus; cytoplasm

Question 48

The effect of red light on plants is to:

A) inactivate phytochrome.
B) convert Pfr to Pr.
C) inhibit germination in some seeds.
D) initiate shade avoidance responses.
E) impact the equilibrium between Pr and Pfr.

Question 49

PhyB may inhibit flowering in:

A) day-neutral plants.
B) vernalized plants.
C) long-day plants.
D) senescing plants.
E) short-day plants.

Question 50

The photorecepter ____ was first discovered in plants but later found to also be present in fruit flies and mice.

A) Pfr
B) Pr
C) phytochrome
D) cryptochrome
E) PIF3

Question 51

An example of a short-day plant is:

A) poinsettia.
B) sunflower.
C) spinach.
D) coleus.
E) corn.

Question 52

In a hypersensitive response, ____.

A) long-lasting resistance is built up throughout the plan.
B) the axillary buds break dormancy
C) cryptochrome is synthesized
D) jasmonic acid activates enzymes
E) the infected area is sealed off by necrotic lesions

Question 53

____ is a lipid-derived hormone produced in response to the presence of insect pests.

A) Cytokinin
B) Abscisic acid
C) Jasmonic acid
D) Gibberellin
E) Auxin

Question 54

During the day, the leaves of bean plants are ____, and at night they are ____.

A) horizontal; wilted
B) horizontal; vertical
C) horizontal; horizontal
D) vertical; vertical
E) vertical; horizontal

Question 55

Which of the following sequences correctly represents the phytochrome signal transduction pathway?

A) red light → PIF3 activation → PIF3 into nucleus → light-responsive gene switched off
B) red light → Pfr to Pr → Pr into nucleus → Pr-PIF3 complex → light-responsive gene regulation
C) UV light → PIF3 into nucleus → light responsive gene produces phytochrome → Pr to Pfr
D) blue light → Pfr into nucleus → Pfr-PIF3 complex → light-responsive gene regulation
E) red light → Pr to Pfr → Pfr into nucleus → Pfr-PIF3 complex → light-responsive gene regulation

Question 56

Any response of a plant to the relative lengths of light and darkness is referred to as:

A) gravitropism.
B) photoperiodism.
C) phototropism.
D) thigmotropism.
E) thigmomorphogenesis.

Question 57

Figure 38-2 Refer to the accompanying figure. What does the photoperiodic response of the plant in Row A suggest?

A) A brief dark period is the light cue that induces flowering.
B) A brief daylight period is the light cue that induces flowering.
C) A long uninterrupted daylight period is the light cue that induces flowering.
D) A long uninterrupted dark period is the light cue that induces flowering.
E) A determination cannot be made from the data provided.

Question 58

Which statement about cryptochrome is false ?

A) It is implicated in resetting the biological clock.
B) It is a "clock protein."
C) It absorbs green light.
D) Its counterparts are found in fruit flies and mice.
E) It sometimes interacts with phytochrome.

Question 59

What happens after the sun goes down?

A) The level of Pfr increases.
B) The level of Pfr remains constant.
C) Pfr is converted to Pr.
D) Pfr is degraded.
E) Pr is converted to Pfr.

Question 60

The photoreceptor for photoperiodism and some other light-initiated plant responses is a group of blue-green pigments named:

A) xanthophyll.
B) carotene.
C) chlorophyll.
D) phytochrome.
E) phycocyanin.

Question 61

Describe the evidence for the existence of a flowering promoter and also for the existence of a flowering inhibitor.

Question 62

Jasmonic acid is structurally similar to prostaglandins .

Question 63

Methyl salicylate triggers the genes that code for the systemic acquired resistance pathway .

Question 64

A long day plant will flower when exposed to short nights.

Question 65

A circadian rhythm has a period that approximates a(n) 12-hour cycle.

Question 66

Write a one-sentence explanation for the role of each of the following plant hormonelike signaling molecules: methyl salicylate and jasmonic acid.

Question 67

The site of gravity perception in roots is the root apical meristem .

Question 68

In three sentences or less, explain why a plant placed in a window grows toward the light.

Question 69

Pr strongly absorbs light having a wavelength of 730 nm.

Question 70

Ethylene stimulates the ripening of fruits.

Question 71

____ helps defend plants against viral infection.

A) Systemin
B) Jasmonates
C) Brassinosteroids
D) Methyl salicylate
E) Oligosaccharins

Question 72

When cytokinins are sprayed on leaves of a cut stem, the leaves become, or remain, yellow .

Question 73

Phototropins are light-activated kinases .

Question 74

Summarize the effects of each of the six classes of plant hormones.

Question 75

Differentiate between circadian rhythms and photoperiodism. Give examples of each. What regulates these responses?

Question 76

Auxin produced by the apical meristem inhibits the germination of lateral buds.

Question 77

The twining of tendrils around a support is an example of thigmomorphogenesis .

Question 78

Cryptochrome absorbs blue light.

Question 79

Summarize the experiment by Darwin that provided the first evidence for auxins.

Question 80

When Pfr absorbs far-red light, the Pfr is converted to Pr.