Deck 26: Plant Growth and Development

Question 1

In apple plants,cotyledons protect the shoot of the seedling as it grows.Eventually,the plant becomes a small deciduous tree that produces large pomaceous fruits (the apple).Based on this developmental course,one can infer that

A) apple plants are evergreen.
B) the apple lacks apical dominance.
C) the apple is a monocot.
D) the apple is a eudicot.
E) apple hormones are produced by specialized glands.

Answer 1

D

Question 2

Which process 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

Answer 2

C

Question 3

Seeds of a plant that is native to Mexico are released in mid-spring just as their native habitat is drying out and becoming unfavorably hot.They are dormant after they are released.This example demonstrates that seed dormancy usually helps 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 for seed germination.
E) many seeds are ready to germinate.

Answer 3

B

Question 4

As a seed undergoes the early stages of germination,its water content will _______ and its water potential will become _______ negative.

A) increase;more
B) increase;less
C) stay the same;more
D) stay the same;less
E) decrease;more

Question 5

The pre-photosynthetic 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 6

Which step is initially most crucial for the survival of a growing seedling that has germinated an inch underground?

A) Production of chlorophyll
B) Rapid elongation of the shoot
C) Breaking of dormancy
D) Rapid start of photosynthesis
E) Expansion of cotyledons

Question 7

Plant primary roots typically grow into the ground by responding to the directional signal of gravity.If you wanted to identify a plant that had a mutation in its gravity signal transduction pathway,which method would be most useful?

A) Growing a batch of seeds in zero-gravity conditions and then collecting any seedlings with primary roots that are growing in different directions
B) Treating a batch of seeds with a mutagen,placing each germinating seed on the soil with the primary roots emerging in a different direction,and collecting any plants with primary roots that grow into the soil
C) Treating a batch of seeds with a mutagen,growing them alongside wild-type seeds,and collecting any seedlings with primary roots growing longer than the wild-type roots
D) Growing a batch of seeds in zero-gravity conditions and then collecting any seedlings with primary roots that are growing toward the ground
E) Treating a batch of seeds with a mutagen,growing them alongside wild-type seeds,and collecting any seedlings with primary roots growing in a direction that is different from that of the wild-type roots

Question 8

A scientist receives a seed sample from a plant growing in an unknown location and discovers that prolonged cold treatment is needed to break seed dormancy.This suggests that in the native habitat of the plant,the colder part of the year

A) occurs right before the best growing season.
B) is favorable for growth.
C) lasts for several months.
D) is brief.
E) None of the above

Question 9

If you were conducting a study to determine how seeds from various habitats break dormancy,which experimental variable would be least useful?

A) Fire
B) Low oxygen levels
C) Cycles of freezing and thawing
D) Washing away of inhibitor molecules
E) Variations in soil microorganisms

Question 10

Which method is most useful for studying plant signal transduction pathways?

A) Genetic screens of mutants
B) Extensive field tests
C) Careful analysis of seeds
D) Extensive planting programs
E) Data collection in the wild

Question 11

You are given a sample of seeds to analyze and are told that the germination process may have begun.If this is the case,the seeds will

A) be dehydrated.
B) have been placed in the ground and then removed for analysis.
C) have imbibed water.
D) have high levels of abscisic acid.
E) be dormant.

Question 12

A researcher studying a seedling can determine its stage of development according to the molecular phenomena that are occurring.If DNA synthesis is observed,the seedling is at the stage at which

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

Question 13

A scientist is studying seeds from a species of sundew native to Western Australia.These seeds need to be treated with smoke before they can imbibe and germinate.This suggests that _______ in order for the seeds to germinate.

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

Question 14

In order to respond to environmental stimuli,plants employ sequences of biochemical reactions called

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

Question 15

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) allow the seed to avoid competition.
D) increase the likelihood of dispersal.
E) All of the above

Question 16

Which sequence represents the correct order of the stages of seed germination and subsequent events?

A) Imbibition $\rightarrow$ RNA synthesis $\rightarrow$ cell division $\rightarrow$ starch degradation
B) Imbibition $\rightarrow$ starch degradation $\rightarrow$ cell division $\rightarrow$ RNA synthesis
C) Starch degradation $\rightarrow$ RNA synthesis $\rightarrow$ cell division $\rightarrow$ imbibition
D) Starch degradation $\rightarrow$ RNA synthesis $\rightarrow$ imbibition $\rightarrow$ cell division
E) Imbibition $\rightarrow$ RNA synthesis $\rightarrow$ starch degradation $\rightarrow$ cell division

Question 17

What part of the weight of a dormant seed is water?

A) 3-10 percent
B) 5-15 percent
C) 20-30 percent
D) 40-60 percent
E) 60-70 percent

Question 18

A botanist is trying to isolate all of the auxin produced in a bean plant by extracting it from seedlings in a range of developmental stages.Which aspect of plant hormones must the scientist take into consideration while planning the extraction protocol?

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

Question 19

A biology class studying plant development is observing the germination of orange seeds.What structure are they most likely to observe emerging first from the seed coat?

A) Hypocotyl
B) Epicotyl
C) Coleoptile
D) Cotyledon
E) Radicle

Question 20

What molecule is most critical for the germination of all seeds?

A) Glucose
B) Water
C) DNA
D) Protein
E) None of the above

Question 21

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 primarily transported in only one direction in the plant.
D) moves in a direction away from the light.
E) cannot move through gelatin unless it is bound to a polar molecule.

Question 22

All of the following may serve to break dormancy and initiate seed germination except

A) abrasion.
B) fire.
C) exposure to water.
D) treatment with abscisic acid.
E) treatment with gibberellic acid.

Question 23

Which sequence represents the correct order of events that cause auxin to move in a polar direction in a plant stem?

A) The ionized auxin is transported into the cell by efflux carriers,the auxin gains a proton in the basic cytosol,and the non-ionized auxin passively diffuses out of the base of the cell.
B) Auxin picks up a proton in the basic cell wall space,the non-ionized auxin passively diffuses across the cell membrane into the cell,the auxin loses a proton in the more acidic cytosol,the ionized auxin is transported out of the cell by an efflux carrier located only at the base of the cell,and the proton pumps in the cell membrane acidify the cell wall space.
C) Auxin passively diffuses into the cell as an anion,auxin stimulates proton pumps in the cell membrane to acidify the cytosol,the auxin picks up a proton to become uncharged,and the non-ionized auxin is actively transported out of the cell by efflux carriers.
D) Proton pumps in the cell membrane acidify the cell wall space,auxin picks up a proton in the acidic cell wall space,the non-ionized auxin passively diffuses across the cell membrane into the cell,the auxin loses a proton in the more basic cytosol,and the ionized auxin is transported out of the cell by an efflux carrier located only at the base of the cell.
E) Auxin moves down its concentration gradient from the tip of the plant where it is made to the base where it is used,passively entering and exiting each cell along the way.

Question 24

Suppose that botanists have discovered a new plant hormone and they hypothesize that it is required for normal leaf shape.Which experimental result would not support this hypothesis?

A) A mutant with abnormal leaf shape is found to lack the hypothesized hormone.
B) A chemical that is isolated is found to affect leaf shape when applied to the young tip of developing plants.
C) Plants in which the synthesis of the hypothesized hormone is inhibited develop abnormal leaves.
D) Removal of the young tip of the plant causes the development of abnormal leaf shape.
E) Treatment of a leaf-shape mutant plant with the hypothesized hormone restores normal leaf development.

Question 25

Which part of a seedling is sensitive to light?

A) The entire seedling
B) The entire shoot above the roots
C) The entire coleoptile
D) The coleoptile region several millimeters below the tip
E) The tip of the coleoptile

Question 26

The increasing popularity of small home vegetable gardens over the last century has increased the need for smaller,dwarf cultivars of various vegetables such as peas and tomatoes.In general,these dwarfs produce less _______ than their wild-type counterparts.

A) auxin
B) cytokinin
C) gibberellic acid
D) ethylene
E) brassinosteroid

Question 27

A new variety of geranium is found that,unlike other members of the genus,grows for a year as a squat,short plant and then rapidly elongates its stem to produce a tall stem with many flowers.What hormone is most likely produced in large amounts just before the elongating of the stem?

A) Auxin
B) Abscisic acid
C) Gibberellins
D) Ethylene
E) Cytokinins

Question 28

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 29

Suppose that seedless raspberries have been discovered in a mutant screen and commercialized.What plant hormone could be added to the developing fruits to make them grow to the normal size of seeded fruits?

A) Cytokinins
B) Nitrous oxide
C) Ethylene
D) Abscisic acid
E) Gibberellins

Question 30

You are observing a seed that has recently increased greatly in size and metabolic rate.What process has caused these changes?

A) Imbibition
B) Elongation
C) Activation
D) Ripening
E) None of the above

Question 31

You remove the cotyledons from a seed,but the embryo still grows normally for the first few days.The most likely reason is that

A) the seed has its reserves in the endosperm.
B) the embryo has extra,hidden cotyledons.
C) the seed contains a fungal symbiont.
D) the embryo is digesting the seed coat to replace the missing cotyledons.
E) the seed contains digestible pigments in its roots.

Question 32

Auxin polar transport goes

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

Question 33

Beer breweries use gibberellins to ensure consistent germination and liberation of sugars from starch in grain endosperm.Which layer of the grain responds to the applied gibberellins?

A) Mesophyll
B) Cotyledon
C) Aleurone
D) Seed coat
E) Embryo

Question 34

In promoting normal germination (and also in brewing,when production of sugars for alcoholic fermentation is desired),gibberellins

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

Question 35

Gibberellins were discovered by the biologist Eiichi Kurosawa while he was studying a 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 36

Evidence that gibberellins are produced by plants was gathered in studies with dwarf mutant strains of tomato.Work on dwarf peas produced the same results: 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 37

Whereas gibberellins promote seed germination,_______ promote(s)dormancy.

A) auxin
B) cytokinins
C) abscisic acid
D) brassinosteroids
E) ethylene

Question 38

Auxin's polar transport relies in part on the fact that auxin is a weak acid that

A) binds H⁺ in high pH conditions.
B) ionizes to release H⁺ in neutral pH conditions.
C) forms a base in the cell wall.
D) is passively transported across cells.
E) pumps protons across the cell membrane.

Question 39

Proton pumps within a cell tend to make the inside of the cell _______ acidic than the outside,and the outside of the cell _______ acidic than the inside.

A) more;more
B) more;less
C) less;more
D) less;less
E) None of the above;proton pumps do not affect the acidity levels of a cell.

Question 40

A botanist compares a wild-type plant to two different mutant plants of the same species.One of the mutants is small and has fewer cells than the wild type.The other has the normal number of cells,though each cell is much smaller than the cells in the wild-type plant.Which hormones are likely to be missing or not functioning properly in these two types of mutants?

A) Cytokinins and gibberellins
B) Auxin and gibberellins
C) Ethylene and gibberellins
D) Gibberellins and brassinosteroids
E) Cytokinins and abscisic acid

Question 41

Apical dominance is most strengthened by

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

Question 42

In cell cultures,root formation can be promoted by _______ auxin concentrations and _______ concentrations.

A) decreasing;increasing gibberellin
B) increasing;decreasing cytokinin
C) increasing;decreasing gibberellin
D) decreasing;increasing cytokinin
E) increasing;increasing cytokinin

Question 43

Which plant hormone stimulates axillary buds to grow into branches?

A) Abscisic acid
B) Auxin
C) Cytokinins
D) Ethylene
E) Gibberellins

Question 44

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

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

Question 45

Which statement about plant tropisms is true?

A) An imbalance in gibberellin 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 gravity receptor.
E) Auxin is the gravity receptor.

Question 46

Leaf abscission involves

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

Question 47

Gravitropism would not be observed in a plant grown in a weightless environment,because gravitropism is the phenomenon by which a plant part grows

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

Question 48

A botanist places an agar block containing auxin on the cut top surface of a sunflower seedling,positioning it off-center.If the auxin,as expected,diffuses into the stem as if it had come from the tip of the coleoptile,what is the botanist likely to find after a day has passed?

A) The sunflower has grown straight up.
B) The sunflower has grown and bent away from the side with the block.
C) The sunflower has grown and bent toward the side with the block.
D) The sunflower has failed to grow.
E) The sunflower has died.

Question 49

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

A) flowers that lack embryos.
B) seeds that lack embryos.
C) fruit with only one seed instead of many.
D) fruit without fertilization.
E) an embryo without fertilization.

Question 50

The gibberellin signal transduction pathway leads to

A) the inhibition of the polyubiquitination of repressor proteins.
B) the inactivation of growth-stimulating genes.
C) the inactivation of proteases.
D) protein breakdown to allow for gene expression.
E) All of the above

Question 51

To stop the growth of a plant cell effectively,the most useful procedure is to stop

A) the binding of water to the cell.
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) proton-pumping into the cytoplasm.

Question 52

It was discovered recently that both auxin and gibberellins have specific protein receptors which,when bound by hormones,

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

Question 53

Which mutation would most likely damage a plant's ability to respond to light or to gravity?

A) A mutation that reduced activity of the proton pump
B) A mutation that enhanced activity of the proton pump
C) A mutation that disabled movement of ubiquitin
D) A mutation that changed the absorption spectrum for phototropin
E) A mutation that disabled movement of the auxin anion efflux carriers

Question 54

Radishes provide a good demonstration of the pronounced swelling that cytokinins can cause in

A) roots.
B) stems.
C) leaves.
D) flowers.
E) buds.

Question 55

Auxins are plant hormones that affect

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

Question 56

Loosening of the plant cell wall for expansion is promoted by

A) cellulose molecules.
B) high pH.
C) acid-activated expansins.
D) water uptake by the vacuole.
E) cross-linking polymers.

Question 57

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 58

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 59

This new genetic variant displays which characteristic?

A) Parthenocarpy
B) Increased abscission
C) Decreased abscission
D) Increased apical dominance
E) Decreased apical dominance

Question 60

Which characteristic is the most likely cause of the new variant's phenotype?

A) Increased expression of auxin
B) Increased expression of an auxin inhibitor
C) Increased expression of gibberellins
D) Increased expression of a gibberellin inhibitor
E) Altered location of the expression of gibberellins

Question 61

Phototropin is a

A) type of phytochrome.
B) type of hormone receptor.
C) type of hormone.
D) blue-light receptor.
E) transcription factor.

Question 62

Which statement correctly describes the signal transduction pathway initiated by the binding of cytokinins to its receptor protein?

A) Protein kinase activity occurs at the cytoplasmic end of the receptor,leading to activation of effectors.
B) Protein kinase activity occurs at the extracellular end of the receptor,leading to activation of transcription factors.
C) Transcription factors are activated,leading to activation of effectors.
D) Gene transcription leads to production of more receptor proteins.
E) The cytokinin‒receptor complex enters the nucleus,leading to gene expression.

Question 63

All of the following are plant hormones except

A) abscisic acid.
B) brassinosteroids.
C) cytokinins.
D) gibberellins.
E) phytochrome.

Question 64

A scientist is studying the signals that promote seed germination in a newly discovered desert shrub.Moistening the seeds with various hormones and varying the temperature do not cause the seeds to germinate.What would be the best germination-inducing signal to try next?

A) Red light
B) Abscisic acid
C) Starches
D) Blue light
E) Friction

Question 65

The production of auxin in response to light involves

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

Question 66

Commercial preparations of _______ can be applied to cereal grains in order to _______.

A) abscisic acid;soften them
B) abscisic acid;prevent seed germination
C) auxins;prevent seed germination
D) auxins;cause parthenocarpy
E) gibberellins;soften them

Question 67

The protein pigment phytochrome is thought to allow plants to detect photoperiod because

A) it can be converted into two different forms,depending on the specific wavelengths of light that it absorbs.
B) it absorbs red light during the day and breaks down in darkness.
C) the photoperiod response depends on how much light is absorbed by phytochrome.
D) the pigment becomes inactive in the dark.
E) the pigment response can be observed only in intact living plants.

Question 68

Which statement about phytochrome P_r is true?

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

Question 69

The physiologically active form of phytochrome

A) is P_fr.
B) is P_r.
C) is located in the cell membrane.
D) absorbs red light.
E) is 730 nm in diameter.

Question 70

A plant's bushiness is promoted by a _______ ratio.

A) high auxin-to-gibberellin
B) low auxin-to-gibberellin
C) high auxin-to-cytokinin
D) low auxin-to-cytokinin
E) high gibberellin-to-cytokinin

Question 71

An unripe lemon that is placed in a paper bag with an apple will ripen: its skin will yellow,it will soften,and it will produce the characteristic lemon odor.Which plant hormone released by the apple causes this effect?

A) Auxin
B) Ethylene
C) Cytokinins
D) Gibberellins
E) Abscisic acid

Question 72

Florists use silver thiosulfate to

A) delay abscission of petals caused by the action of auxin.
B) delay abscission of leaves caused by the action of abscisic acid.
C) keep petals from turning brown due to the action of ethylene.
D) keep leaves green longer by promoting the action of cytokinins.
E) prevent microbial decay of senescing leaves and petals.

Question 73

A researcher who wishes to experimentally manipulate leaf senescence in tobacco would apply _______ to promote senescence and _______ to delay it.

A) auxin;cytokinins
B) ethylene;gibberellins
C) ethylene;auxin
D) cytokinins;auxin
E) cytokinins;ethylene

Question 74

Which process is not affected by ethylene?

A) Breakdown of fruit cell walls
B) Promotion of leaf abscission
C) Ripening of fruit
D) Inhibition of stem elongation
E) Opening of the eudicot apical hook

Question 75

Which plant hormone is a gas?

A) Cytokinins
B) Abscisic acid
C) Gibberellins
D) Auxin
E) Ethylene

Question 76

Unlike other plant hormones,ethylene

A) is not produced by all plants.
B) is a steroid.
C) inhibits root expansion.
D) acts strictly as a promoter.
E) is a gas.

Question 77

Which sequence represents the correct order of events in cytokinin signal transduction?

A) Cytokinin is produced $\rightarrow$ cytokinin binds to its receptor protein $\rightarrow$ cytoplasmic steps are initiated $\rightarrow$ transcription factor is activated
B) Cytokinin is produced $\rightarrow$ cytoplasmic steps are initiated $\rightarrow$ transcription factor is activated $\rightarrow$ cytokinin binds to its receptor protein
C) Cytokinin binds to its receptor protein $\rightarrow$ cytoplasmic steps are initiated $\rightarrow$ transcription factor is activated $\rightarrow$ cytokinin is produced
D) Cytokinin binds to its receptor protein $\rightarrow$ transcription factor is activated $\rightarrow$ cytokinin is produced $\rightarrow$ cytoplasmic steps are initiated
E) Cytoplasmic steps are initiated $\rightarrow$ transcription factor is activated $\rightarrow$ cytokinin is produced $\rightarrow$ cytokinin binds to its receptor protein

Question 78

In plant seeds that germinate in response to a brief pulse of light,_______ is most effective in triggering germination.

A) green light
B) far-red light
C) red light
D) the initiation of photosynthesis
E) red light followed by far-red light

Question 79

If a mutant plant were created that lacked the receptor for ethylene,its leaves would

A) not expand as much as wild-type leaves.
B) be unable to turn green in the spring.
C) produce excess cytokinins to compensate for the missing ethylene response.
D) be unable to undergo abscission in the fall.
E) None of the above

Question 80

Shortly after sundown after a long sunny day,the concentrations of the P_r isoform are

A) high and increasing.
B) high and stable.
C) high and decreasing.
D) low and increasing.
E) low and decreasing.