Deck 38: Plant Developmental Responses to External and Internal Signals

Question 1

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

Answer 1

A

Question 2

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.

Answer 2

E

Question 3

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 3

B

Question 4

You expose a plant to a light that shines on the right side of a plant. Which statement best explains 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.

Question 5

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 6

In barley seed germination, which of the following is true?

A) The aleurone cells determine when germination occurs by secreting α-amylase.
B) The aleurone cells determine when germination occurs by secreting gibberellin.
C) The embryo determines when germination occurs by secreting α-amylase.
D) The embryo determines when germination occurs by secreting abscisic acid.
E) The embryo determines when germination occurs by secreting gibberellin.

Question 7

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 8

Phototropism is the directional growth of a plant caused by ____.

A) gravity
B) light
C) touch
D) pH
E) temperature

Question 9

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 10

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

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

Question 11

____ the synthesis of α-amylase is an enzyme that digests starch in the endosperm.

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

Question 12

Which hormone promotes cell division and delays senescence in plants?

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

Question 13

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 14

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

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

Question 15

Gibberellins are also involved in _____, the rapid elongation of a floral stalk that occurs naturally in many plants when they initiate flowering.

A) abscission
B) ripening
C) tropisms
D) bolting
E) molting

Question 16

Auxin's most characteristic action is promotion of ______.

A) fruit production
B) stem elongation
C) deed germination
D) abscission
E) cell division

Question 17

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 18

A seedling growing toward a light source 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 19

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

Question 20

Which hormone promotes apical dominance in plants?

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

Question 21

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 22

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

A) Florigen
B) Ubiquitin
C) Jasmonic acid
D) Brassinosteroids
E) Methyl salicylate

Question 23

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

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

Question 24

A plant's growth response to mechanical stress, such as rain or contact with passing animals, is known as

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

Question 25

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

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

Question 26

Frits Went used tiny blocks of agar to show that ____ is made in the tip of _____.

A) gibberellin; cotyledon
B) cytokinin; coleoptile
C) ethylene; apical meristem
D) auxin; coleoptile
E) abscisic acid; cotyledon

Question 27

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

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

Question 28

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 29

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 30

Which hormone stimulates both leaf abscission and fruit ripening?

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

Question 31

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 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 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 34

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 35

Which of the following statements about plant hormones is false ?

A) They are organic compounds that act as highly specific chemical signals.
B) They are effective at extremely low concentrations.
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 can currently be categorized into seven major classes.

Question 36

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 37

Which of the following statements is true?

A) A short-day plant flowers when it is grown under short-night conditions.
B) A short-day plant flowers when exposed to a long night interrupted with a brief flash of red light.
C) A long-day plant does not flower when grown under long-night conditions.
D) A long-day plant flowers when grown under long-night conditions.
E) A long-day plant does not flower when grown under long-night conditions unless the long night is interrupted with a brief flash of red light.

Question 38

Biologists believe that a flower-producing substance called ____ is produced in the leaves and transported to the phloem.

A) auxin
B) florigen
C) brassinosteroid
D) abscisic acid
E) ethylene

Question 39

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

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

Question 40

Which of the following is 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 41

In which organism is phytochrome not found?

A) Plants
B) Bacteria
C) Animals
D) Fungi
E) Slime molds

Question 42

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 43

_____ activates transcription of the gene for the small subunit of ______, an enzyme involved in photosynthesis

A) Phytochrome; chlorophyll
B) Chlorophyll; rubisco
C) Phytochrome; rubisco
D) Rubisco; phytochrome
E) Cytochrome; rubisco

Question 44

Jasmonic acid is structurally similar to ______ in animals.

A) steroid hormones
B) prostaglandins
C) amino acids
D) nucleotides
E) epinephrine

Question 45

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 46

Which statement concerning phytochrome-induced responses is false ?

A) All responses are 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 47

For Arabidopsis and many other plants, ______ and ______ are implicated in resetting the biological clock.

A) phytochrome; cytochrome
B) phycocyanin; cryptochrome
C) phytochrome, cryptochrome
D) cytochrome; chryptochrome
E) phytochrome; kodachrome

Question 48

You shine light at 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 49

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 50

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 51

________ prevent or slow the spread of the initial infection.

A) Axillary buds
B) Casparian strips
C) Phytochromes
D) Immune cells
E) Necrotic lesions

Question 52

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 53

An example of a short-day plant is

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

Question 54

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 55

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 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

An example of a long-day plant is

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

Question 58

The environmental factor that triggers shade avoidance is that plants perceive changes in the ratio of ___ to ___ light that result from the presence of nearby plants.

A) red; green
B) blue; ultraviolet
C) yellow; green
D) red; far-red
E) blue; violet

Question 59

PhyB may inhibit flowering in

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

Question 60

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 61

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

Question 62

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

Question 63

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

Question 64

In two sentences or less, explain what phytochrome and cryptochrome are, and how they differ.

Question 65

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

Question 66

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

Question 67

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

Question 68

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

Question 69

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

Question 70

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

Question 71

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

Question 72

Ethylene stimulates the ripening of fruits.

Question 73

Jasmonic acid is structurally similar to prostaglandins.

Question 74

Cryptochrome absorbs blue light.

Question 75

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

Question 76

Pr strongly absorbs light that has a wavelength of 730 nm.

Question 77

____ helps defend plants against viral infection.

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

Question 78

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

Question 79

Phototropins are light-activated kinases.

Question 80

Summarize the hypersensitive response and system-acquired resistance, and explain how the two differ from each other.