Deck 37: Regulation of Plant Growth

Question 1

Before seed germination can begin,

A) seed dormancy must be broken.
B) the radicle must emerge from the seed.
C) water must be excluded.
D) oxygen must be excluded.
E) cell division must increase greatly.

Answer 1

A

Question 2

Which of the following does not aid in breaking seed dormancy?

A) Fire
B) Low oxygen levels
C) Cycles of freezing and thawing
D) Leaching of inhibitor molecules
E) Soil microorganisms

Answer 2

B

Question 3

Which process is not directly affected by auxin?

A) Apical dominance
B) Leaf abscission
C) Synthesis of digestive enzymes by barley seeds
D) Root initiation
E) Cell elongation

Answer 3

C

Question 4

Which of the following does not increase during the initial stages of seed germination?

A) Cell size
B) Respiration
C) RNA synthesis
D) DNA synthesis
E) Protein synthesis

Question 5

The gibberellins

A) are responsible for phototropism and gravitropism.
B) are gases at room temperature.
C) are produced only by fungi.
D) cause flowering in plants.
E) inhibit the synthesis of digestive enzymes by barley seeds.

Question 6

Which statement about cytokinins is not true?

A) They promote cell division in tissue cultures.
B) They delay the senescence of leaves.
C) They usually promote the elongation of stems.
D) They act by a receptor with protein kinase activity.
E) They were discovered as a breakdown product of DNA.

Question 7

To mobilize its nutrient reserves, a germinating barley seed

A) becomes dormant.
B) undergoes senescence.
C) secretes gibberellins into its endosperm.
D) converts glycerol and fatty acids into lipids.
E) takes up proteins from the endosperm.

Question 8

In coleoptile tissue, auxin

A) is transported from base to tip.
B) is transported from tip to base.
C) can be transported toward either the tip or the base, depending on the orientation of the coleoptile with respect to gravity.
D) is transported by simple diffusion, with no preferred direction.
E) is not transported, because auxin is used where it is made.

Question 9

Phytochrome

A) is the only photoreceptor pigment in plants.
B) exists in two forms interconvertible by light.
C) is a pigment that is colored red or far-red.
D) is a green-light receptor.
E) is the photoreceptor for phototropism in coleoptiles.

Question 10

Which of the following does not occur in seed germination?

A) Imbibition of water
B) Metabolic changes
C) Growth of the radicle
D) Mobilization of nutrient reserves
E) Extensive mitotic divisions

Question 11

Signal transduction for both auxin and gibberellins involves

A) binding of the hormone to a nuclear receptor.
B) degradation of a repressor of gene transcription.
C) production of a small molecule second messenger.
D) light absorption followed by chemical changes.
E) breakdown of the hormone.

Question 12

The adaptive advantage of seed dormancy is that it may

A) result in germination at a favorable time.
B) increase the probability of a seed's germinating in the right place.
C) be a way to avoid competition.
D) result in an increase in the likelihood of dispersal.
E) All of the above

Question 13

The prephotosynthetic seedling must survive using resources from the _______ or the _______.

A) cotyledons; endosperm
B) radicle; hypocotyl
C) foliage leaf; epicotyl
D) seed coat; coleoptile
E) apical hook; secondary roots

Question 14

Ethylene

A) causes the triple response in seedlings growing underground.
B) is liquid at room temperature.
C) delays the ripening of fruits.
D) generally promotes stem elongation.
E) inhibits the swelling of stems, in opposition to cytokinin's effects.

Question 15

Which of the following does not occur during the earliest stages of germination?

A) Intake of water
B) Activation of enzymes
C) Cell division
D) Increase in cellular respiration
E) Mobilization of food reserves

Question 16

Which of the following is not an advantage of seed dormancy?

A) It makes the seed more likely to be digested by birds that disperse it.
B) It counters the effects of year-to-year variations in the environment.
C) It increases the likelihood that a seed will germinate in the right place.
D) It favors dispersal of the seed.
E) It may result in germination at a favorable time of year.

Question 17

Seed dormancy is usually an adaptation to ensure that

A) the embryo is mature.
B) germination occurs at a favorable time.
C) seeds germinate near the parent plant.
D) levels of abscisic acid are high enough.
E) many seeds are ready to germinate.

Question 18

As a seed germinates, DNA synthesis begins

A) when gibberellins are secreted by the embryo.
B) when the embryonic root, or radicle, begins to grow.
C) as imbibition takes place.
D) when the endosperm starts metabolizing starches, proteins, and lipids.
E) when the aleurone layer assembles enzymes, proteases, and ribonucleases.

Question 19

Which of the following is most important for the future survival of a young plant seedling that has not yet been exposed to light?

A) Increased production of chlorophyll
B) Rapid elongation of the shoot
C) Increased production of phytochrome
D) Rapid photosynthesis
E) Increased uptake of water

Question 20

The first (or embryonic) root that emerges from the seed is called the

A) hypocotyl.
B) epicotyl.
C) coleoptile.
D) cotyledon.
E) radicle.

Question 21

As a first step in seed germination, the seed must

A) dehydrate.
B) be placed in the ground.
C) imbibe.
D) be activated by germisin.
E) pump protons.

Question 22

Which of the following enhance(s) energy storage in a small space?

A) Proteins and nucleic acids
B) Lipids and starches
C) Germination inhibitors
D) Sugars and amino acids
E) A highly negative water potential

Question 23

Which of the following suggests that plants produce gibberellins?

A) Genetically dwarf corn seedlings grow tall with gibberellin treatment.
B) Genetically tall corn plants grow even taller with gibberellin treatment.
C) Gibberellins are produced by tall and dwarf varieties of corn.
D) Gibberellins are produced by dwarf varieties of corn.
E) Different varieties of corn produce different gibberellins.

Question 24

The first evidence that gibberellins are produced by plants was gathered in studies with dwarf mutant strains of corn. Treatment with gibberellins caused the dwarf plants to _______, while the normal, tall plants _______.

A) grow taller; also grew taller, but only slightly
B) grow taller; were virtually unaffected
C) stop growing immediately; stopped growing after a period of time
D) stop growing; were virtually unaffected
E) die; stopped growing

Question 25

Spraying biennials such as cabbage with gibberellins causes them to bolt, a process first observed as an increase in

A) leaf senescence.
B) stem elongation.
C) the number of flowers.
D) the size of fruit.
E) the number of seeds per fruit.

Question 26

The F-box in the regulation system of giberellins facilitates

A) protein breakdown to allow for the action of auxin.
B) the inactive state of growth-stimulating genes.
C) the inactivation of proteases.
D) the inhibition of the poly-ubiquitination of repressor proteins.
E) All of the above

Question 27

In a classic experiment, a gelatin block containing auxin was placed on one edge of a decapitated coleoptile. The result was that the coleoptile

A) grew straight up.
B) grew more on the side with the block.
C) grew more on the side away from the block.
D) grew a new coleoptile tip.
E) did not grow.

Question 28

Plant growth substances (hormones) generally

A) have a single specific role.
B) affect mainly the cells that produce them.
C) are species-specific.
D) are produced in many different parts of the plant.
E) elicit rapid responses.

Question 29

Genetic mutations that disrupt plant development are usually studied by means of

A) genetic screens.
B) extensive field tests.
C) careful analysis of seeds.
D) extensive planting programs.
E) data collection in the wild.

Question 30

In the experiments of Charles and Francis Darwin, which parts of the seedlings were shown to be sensitive to light?

A) The entire seedling
B) The entire shoot above the roots
C) The entire coleoptile
D) The coleoptile just below the tip
E) The extreme tip of the coleoptile

Question 31

The discovery of auxin can be traced back to the work of Charles and Francis Darwin and their studies of

A) photosynthesis.
B) photorespiration.
C) photophosphorylation.
D) phototropism.
E) photoperiodism.

Question 32

To be able to respond to environmental stimuli at any stage of development, plants employ sequences of biochemical reactions called

A) signal transduction pathways.
B) cellular responses.
C) regulation.
D) mutations.
E) abscission.

Question 33

As a grass seed germinates, the embryonic plant secretes gibberellins, which

A) absorb light.
B) cause stem elongation.
C) mobilize stored foods.
D) take up water.
E) direct the shoot upward.

Question 34

Gibberellins were discovered by the biologist Eiichi Kurosawa while he was studying the "foolish seedling" disease of _______, in which seedlings_______.

A) corn; grow unusually slowly
B) rice; grow into tall, spindly plants
C) wheat; die after germination
D) barley; produce seeds unusually early
E) millet; have a beneficial mutation

Question 35

In their experiment with grass coleoptiles, Charles and Francis Darwin observed that the photoreceptor was _______ and the bending took place _______.

A) in the tip; also at the tip
B) below the tip; also below the tip
C) in the tip; below the tip
D) below the tip; throughout the coleoptile
E) in the tip; throughout the coleoptile

Question 36

To make seedless grapes grow to normal size, growers spray or treat them with

A) cytokinins.
B) nitric oxide.
C) ethylene.
D) auxin solution.
E) gibberellin solution.

Question 37

In addition to hormones, _______ regulate the growth of plants.

A) photoreceptors
B) lipids
C) starches
D) mutations
E) germination inhibitors

Question 38

Which of the following does not serve to break dormancy and initiate seed germination?

A) Scarification by abrasion
B) Scarification by fire
C) Exposure to water
D) Abscisic acid
E) Growth promoters

Question 39

Giberellins are plant hormones that affect

A) stem growth.
B) fruit size.
C) seed germination.
D) All of the above
E) None of the above

Question 40

Bolting, or rapid stem elongation, is induced by

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

Question 41

Experimental removal of the auxin source demonstrates that leaf abscission is _______ by auxin and apical dominance is _______ by auxin.

A) promoted; also promoted
B) inhibited; also inhibited
C) promoted; inhibited
D) inhibited; promoted
E) promoted; unaffected

Question 42

The movement of auxin in plants is said to be "polar," which means that auxin

A) is a chemically polar molecule.
B) is produced only in one part of the plant.
C) is transported from the tip to the base of the plant.
D) moves away from the light.
E) cannot move through gelatin.

Question 43

In shoot phototrophic responses, auxin is transported _______ and _______ from the apical meristem.

A) down; asymmetrically
B) down; symmetrically
C) upward; symmetrically
D) evenly; toward the roots
E) upward; toward the tip

Question 44

Cytokinins are most abundant in which area of the plant?

A) Tips of the shoot
B) Leaves
C) Stems
D) Roots
E) Lateral buds

Question 45

The growth of a plant cell is driven primarily by

A) cytokinesis.
B) the uptake of water into the vacuole.
C) the strengthening of cell wall components.
D) the deposition of new cell wall materials on the outside of the cell wall.
E) the forces in transpirational pull.

Question 46

The "wall-loosening factor" from the cytoplasm is now believed to be

A) auxins.
B) cellulose-digesting enzymes.
C) starch-digesting enzymes.
D) expansins.
E) calcium ions.

Question 47

Which of the following is an example or characteristic of plant tropisms?

A) An imbalance in ethylene concentration causes curvature.
B) Roots grow toward the light.
C) One side of the root or shoot grows more rapidly than the other.
D) DNA is the light receptor or gravity receptor.
E) Auxin is the light receptor or gravity receptor.

Question 48

The two-component cytokinin signal transduction pathway in plants is similar to that of

A) viruses.
B) fungi.
C) many animals.
D) bacteria.
E) All of the above

Question 49

Treatment of some plants with gibberellins or auxin causes parthenocarpy, which is the

A) formation of flowers with petals in multiples of four.
B) division of one shoot into two separate shoots.
C) formation of fruit with only one seed instead of many.
D) formation of fruit without fertilization.
E) formation of an embryo without fertilization.

Question 50

Gravitropism is the phenomenon by which a plant part grows

A) toward the center of Earth.
B) in a direction determined by gravity.
C) in a direction opposite to that of the main light source.
D) in a direction opposite to that of the growth of the shoot.
E) toward the darkest area.

Question 51

Auxin transport goes

A) from apex to base.
B) from base to apex.
C) either from apex to base or from base to apex.
D) primarily from apex to base, but sometimes in reverse.
E) primarily from base to apex, but sometimes in reverse.

Question 52

Auxins are plant hormones that affect

A) root initiation.
B) leaf abcission.
C) apical dominance.
D) cell expansion.
E) All of the above

Question 53

Recently, it has been discovered that both auxin and gibberellins have specific protein receptors which, when bound by hormone,

A) inactivate certain gene repressors in the nucleus.
B) activate certain gene repressors in the nucleus.
C) initiate a protein kinase cascade.
D) activate protein pumps in the plasma membrane.
E) acidify the cell wall.

Question 54

Leaf abscission is the

A) separation of leaves from stems.
B) orientation of a leaf toward the light.
C) regeneration of a leaf after a wound.
D) maturation of leaf tissue.
E) initiation of new tissue growth.

Question 55

What is the difference between the cytokinins kinetin and zeatin?

A) Kinetin is found only in aged DNA, whereas zeatin is found only in fresh DNA.
B) Kinetin is the active form of zeatin.
C) Zeatin is the active form of kinetin.
D) Only zeatin is a naturally occurring plant cytokinin.
E) Zeatin is a synthetic cytokinin, whereas kinetin is natural.

Question 56

A cell wall is a network of cross-linked _______ in a matrix of _______ fibers.

A) cellulose molecules; starch
B) starches; polysaccharide
C) polysaccharides and proteins; cellulose
D) starches; nonpolysaccharide
E) cellulose molecules; protein

Question 57

After a few days, a houseplant that has been accidentally knocked on its side will produce shoots that are growing upward relative to its new position. This phenomenon is called

A) positive gravitropism.
B) negative gravitropism.
C) positive phototropism.
D) negative phototropism.
E) positive thigmotropism.

Question 58

Auxins cause elongation by

A) triggering proton release.
B) indirectly activating expansins.
C) indirectly increasing plasticity.
D) All of the above
E) None of the above

Question 59

The likely result of treating a shoot cutting with auxin would be

A) extensive root production.
B) suppression of apical dominance.
C) the growth of lateral buds.
D) bolting of the shoot.
E) nothing.

Question 60

The phenomenon of apical dominance is strengthened most by

A) removal of the tip.
B) auxin production.
C) removal of leaves.
D) production of fruits.
E) removal of fruits.

Question 61

Two different hormones have opposing effects on senescence: _______ promotes it, whereas _______ inhibits it.

A) auxin; cytokinin
B) ethylene; cytokinin
C) ethylene; auxin
D) cytokinin; auxin
E) cytokinin; ethylene

Question 62

Use the following to answer questions:
Match the appropriate plant hormone from the list below with each description that follows. Each hormone may be used once, more than once, or not at all.
a. Abscisic acid
b. Auxin
c. Cytokinin
d. Ethylene
e. Gibberellin
The ripening hormone

Question 63

Unlike other plant hormones, ethylene

A) is not produced by all plants.
B) exerts a number of effects.
C) inhibits plant development.
D) acts either as an inhibitor or a promoter.
E) is a gas.

Question 64

Production of auxin in response to light most likely involves

A) phytochrome.
B) photoreceptors.
C) a mechanism that is currently unknown.
D) phototropin.
E) Both a and b

Question 65

Growth of a shoot tip toward the light, which is called _______, is thought to be mediated by the actions of the hormone _______.

Question 66

It is thought that auxins control growth by cell _______, whereas cytokinins cause growth by cell _______.

Question 67

A protein pigment called phytochrome is thought to monitor photoperiod because

A) it is converted between two forms by specific wavelengths of light.
B) it absorbs red light and breaks down in darkness.
C) the photoperiod response depends on how much light it absorbs.
D) in darkness the pigment becomes inactive.
E) the pigment response can be observed only in intact living plants.

Question 68

Radishes are examples of cytokinins affecting _______ by causing pronounced swelling.

A) roots
B) stems
C) leaves
D) vegetative apical meristem
E) floral apical meristem

Question 69

A germinating grass seedling embryo produces _______, which mobilize stored nutrients.

Question 70

Which of the following is not a plant hormone?

A) Abscisic acid
B) Brassinosteroid
C) Cytokinin
D) Gibberellin
E) Phytochrome

Question 71

Molecules that are active at small concentrations and regulate plant development are called _______.

Question 72

Use the following to answer questions:
Match the appropriate plant hormone from the list below with each description that follows. Each hormone may be used once, more than once, or not at all.
a. Abscisic acid
b. Auxin
c. Cytokinin
d. Ethylene
e. Gibberellin
A gas

Question 73

Use the following to answer questions:
Match the appropriate plant hormone from the list below with each description that follows. Each hormone may be used once, more than once, or not at all.
a. Abscisic acid
b. Auxin
c. Cytokinin
d. Ethylene
e. Gibberellin
Stimulates axillary buds to grow into branches

Question 74

Which of the following processes is not increased by ethylene?

A) Breakdown of fruit cell walls
B) Stimulation of leaf abscission
C) Ripening of fruit
D) Inhibition of stem elongation
E) Change in leaf color from green to red or yellow

Question 75

Which of the following statements about phytochrome P_r is true?

A) It absorbs green light.
B) It looks red in a test tube.
C) It is the active form of phytochrome.
D) It converts spontaneously to the other form in the dark.
E) It controls a variety of plant responses.

Question 76

Phototropin is classified as a(n)

A) phytochrome.
B) blue-light receptor.
C) gibberellin.
D) cytokinin.
E) abscisic acid.

Question 77

The physiologically active form of phytochrome is

A) P_fr.
B) P_r.
C) G protein.
D) cryptochrome A.
E) 730 nm.

Question 78

Florists use silver thiosulfate to

A) delay abscission of petals caused by the action of ethylene.
B) delay abscission of leaves caused by the action of abscisic acid.
C) keep petals from turning brown because of the action of ethylene.
D) keep leaves green longer.
E) promote flower fertilization.

Question 79

In plants that germinate in response to a brief pulse of light,

A) green light is most effective in triggering germination.
B) far-red light is most effective in triggering germination.
C) far-red light reverses the effect of prior exposure to red light.
D) initiation of photosynthesis is the mechanism for germination.
E) a rise in temperature also triggers germination.

Question 80

A plant grows toward the light when the auxin moves to the side (toward/away from) _______ the light; this has the effect of _______ the cell walls in that region, causing asymmetric growth, and thus, bending.