Deck 31: Plant Responses to Internal and External Signals

Question 1

Charles and Francis Darwin concluded from their experiments on phototropism by grass seedlings that the part of the seedling that detects the direction of light is the

A)tip of the coleoptile.
B)part of the coleoptile that bends during the response.
C)base of the coleoptile.
D)cotyledon.

Answer 1

A

Question 2

The proton pump plays a critical role on cell growth response by increasing cell wall plasticity to

A)auxin.
B)cytokinin.
C)gibberellin.
D)ethylene.

Answer 2

A

Question 3

The ripening of fruit and the dropping of leaves and fruit are principally controlled by

A)auxins.
B)cytokinins.
C)indoleacetic acid (IAA).
D)ethylene.

Answer 3

D

Question 4

Why do coleoptiles grow toward light?

A)Auxin is destroyed by light.
B)Gibberellins are destroyed by light.
C)Auxin synthesis is stimulated in the dark.
D)Auxin moves away from the light to the shady side.

Question 5

Which of the following plant hormones alters gene expression and causes cells in the zone of elongation to produce proteins quickly?

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

Question 6

Almost all plant cells have the ability to produce abscisic acid.One of the functions of abscisic acid in plants is to

A)stimulate cell elongation.
B)regulate development of fruit.
C)promote stomatal closure during drought stress.
D)delay leaf senescence.

Question 7

Which of the following hormones would be most useful in promoting the rooting of plant cuttings?

A)strigolactones
B)cytokinins
C)gibberellins
D)indolebutyric acid

Question 8

When growing plants in culture,IAA is used to stimulate cell enlargement.Which plant growth regulator has to now be added to stimulate cell division?

A)ethylene
B)indoleacetic acid
C)gibberellin
D)cytokinin

Question 9

The apical bud of a shoot produces ________,resulting in the inhibition of lateral bud growth.

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

Question 10

Which part of the plant structure synthesizes cytokinins primarily?

A)shoot apical meristem
B)roots
C)ripened fruits
D)almost all plant parts

Question 11

The most common natural cytokine is zeatin,and it was first discovered in

A)maize.
B)rice.
C)barley.
D)oats.

Question 12

Auxins are produced mainly in

A)leaves.
B)root tips.
C)shoot tips.
D)fruits.

Question 13

After some time,the tip of a plant that has been forced into a horizontal position grows upward.This phenomenon is related to

A)calcium release from the endoplasmic reticulum of shaded cells.
B)whether the plant is in the northern or southern hemisphere.
C)auxin production in cells receiving red light.
D)auxin movement toward the lower side of the stem.

Question 14

Which of the following most correctly describes the effect of most hormones that control growth and development?

A)individual hormonal action
B)interaction between hormones
C)chemical nature of hormones
D)availability of nutrients

Question 15

Plant hormones produce their effects by

A)altering the expression of genes.
B)modifying the structure of the hormones.
C)modifying the structure of the nuclear envelope membrane.
D)altering the expression of genes and modifying the permeability of the plasma membrane.

Question 16

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)ethylene.

Question 17

________ is produced in roots and moves up the plant in xylem sap to influence organ formation.

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

Question 18

Which of the following plant hormones is responsible for the activation of lateral buds to grow into new branches?

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

Question 19

Which of the following conclusions is supported by the research of both Frits Went 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)Agar contains a chemical substance that mimics a plant hormone.
C)A chemical substance involved in shoot bending is produced in shoot tips.
D)Once shoot tips have been cut,normal growth cannot be induced.

Question 20

The aleurone layer is stimulated to release ________ as a result of gibberellin release from the embryo.

A)amino acids
B)carbohydrates
C)cytokinins
D)amylase

Question 21

Which of the following chemicals functions as a photoreceptor in plants and regulates photoperiodism and responses to seasons?

A)phytochromes
B)auxins
C)gibberellins
D)cytokinins

Question 22

Statoliths are structures that are responsible for

A)phototropism.
B)gravitropism.
C)thigmotropism.
D)dormancy.

Question 23

The application of which of the following hormones would be a logical first choice in an attempt to produce normal growth in mutant dwarf plants?

A)indoleacetic acid
B)cytokinin
C)gibberellin
D)abscisic acid

Question 24

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)CO₂
B)cytokinins
C)ethylene
D)auxin

Question 25

During the process of etiolation,a morphological adaptation in potato plant growth,which of the following activities takes place?

A)expanded and above ground leaves
B)excessive loss of water through stomata
C)extensive root system
D)elongated stems

Question 26

Auxin transports from cell to cell

A)from top to bottom.
B)from the bottom up.
C)from side to side.
D)in multidirectional ways.

Question 27

Which plant hormone affects the response to mechanical stress,senescence,leaf abscission,and fruit ripening?

A)abscisic acid
B)ethylene
C)indoleacetic acid
D)gibberellin

Question 28

Which of the following plant hormones stimulates cell elongation?

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

Question 29

Why are axillary buds often inhibited from growing even though a stem may be actively elongating?

A)The cells of axillary buds respond differently to auxin than stem cells.
B)Axillary buds are high in abscisic acid that prevents elongation.
C)Axillary buds are low in gibberellins.
D)Stem cells lack receptors for auxin.

Question 30

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 produce a hypocotyl.
B)seedlings do not have an etiolation response.
C)seeds require light to germinate.
D)seeds require a higher temperature to germinate.

Question 31

Which of the following best explains both the growth of a vine up the trunk of a tree and the directional growth of a houseplant toward a window?

A)nastic movement
B)taxic movement
C)tropism response
D)morphological response

Question 32

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 33

A short-day plant will flower only when

A)days are shorter than nights.
B)days are shorter than a certain critical value.
C)nights are shorter than a certain critical value.
D)nights are longer than a certain critical value.

Question 34

Which of the following treatments would enhance the level of the P_fr form of phytochrome?

A)exposure to far-red light
B)exposure to red light
C)long dark period
D)inhibition of protein synthesis

Question 35

Gibberellins and auxins play a common role in

A)cell division.
B)cell maturation.
C)apical dominance.
D)stem elongation.

Question 36

Young leaves and developing seeds are the prime sites for ________ synthesis.

A)auxin
B)gibberellin
C)cytokinin
D)ethylene

Question 37

A flash of red light followed by a flash of far-red light given during the middle of the night to a short-day plant will likely

A)cause increased flower production.
B)have no effect upon flowering.
C)inhibit flowering.
D)stimulate flowering.

Question 38

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)alter the amount of energy available to the plant.
C)are modified by soil temperature changes.
D)can reset the biological clock.

Question 39

Which of the following gases in air circulating units inhibits the production of new ethylene in fruits?

A)oxygen
B)carbon dioxide
C)carbon monoxide
D)sulfur dioxide

Question 40

Which of the following plant hormones plays a critical role in breaking seed dormancy?

A)abscisic acid
B)ethylene
C)indolebutyric acid
D)gibberellin

Question 41

Most scientists agree that global warming is under way;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 to improve plant response to and survival of 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 42

Trichomes on certain plant species are a ________ to prevent excessive herbivory.

A)physical defense
B)chemical defense
C)behavioral defense
D)combination of chemical and behavioral defense

Question 43

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 44

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

A)rapid growth response.
B)potassium channels.
C)nervous tissue.
D)aquaporins.

Question 45

Which of the following plant hormones plays a critical role on stomatal closures to avoid wilting?

A)abscisic acid
B)gibberellins
C)ethylene
D)cytokinin

Question 46

The initial response of the root cells of a tomato plant watered with seawater would be to

A)rapidly produce organic solutes in the cytoplasm.
B)rapidly expand until the cells burst.
C)begin to plasmolyze as water is lost.
D)actively transport water from the cytoplasm into the vacuole.

Question 47

What is the probable role of salicylic acid in the defense responses of plants?

A)to destroy pathogens directly
B)to activate the systemic acquired resistance of plants
C)to close stomata,thus preventing the entry of pathogens
D)to activate heat-shock proteins

Question 48

Statoliths are responsible for plants to exhibit

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

Question 49

The hypersensitive response,a nonspecific defense mechanism,of plants prevents the spread of pathogens by producing ________ around the infection site.

A)methyl salicylic acid
B)citric acid
C)succinic acid
D)fumaric acid

Question 50

Which one of the following plants has thigmotropism?

A)Mimosa pudica
B)chrysanthemum
C)rose
D)dandelion

Question 51

A short-day plant exposed to nights longer than the minimum for flowering but interrupted by short flashes of light

A)will never flower.
B)might flower depending upon the duration of the light flash.
C)will not be affected and will flower.
D)might flower depending upon the wavelengths of the light flashes.

Question 52

Plants that have their flowering inhibited by being exposed to bright lights at night are

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

Question 53

A botanist discovers a plant that lacks the ability to form starch grains in root cells,yet the roots still grow downward.This evidence refutes the long-standing hypothesis that

A)falling statoliths trigger gravitropism.
B)starch accumulation triggers the negative phototropic response of roots.
C)starch grains block the acid growth response in roots.
D)starch is converted to auxin,which causes the downward bending in roots.

Question 54

A plant will recognize a pathogenic invader

A)if it has many specific plant disease resistance (R)genes.
B)when the pathogen has an R gene complementary to the plant's antivirulence (Avr)gene.
C)only if the pathogen and the plant have the same R genes.
D)if it has the specific R gene that corresponds to the pathogen molecule encoded by an Avr gene.

Question 55

If the range of a species of plants expands to a higher latitude,which of the following processes is the most likely to be modified by natural selection?

A)circadian rhythm
B)photoperiodic response
C)phototropic response
D)biological clock

Question 56

Which of the following is the most likely plant response to an attack by herbivores?

A)leaf abscission to prevent further loss
B)early flowering to try to reproduce before being eaten
C)production of chemical compounds for defense or to attract predators
D)production of physical defenses,such as thorns

Question 57

Which plant organ detects changes in the photoperiod and produces signaling molecules that cue buds to develop as flowers?

A)stem
B)petiole
C)root
D)leaf

Question 58

You are part of a desert plant research team trying to discover crops that will be productive in arid climates.You discover a plant that produces a hormone under water-deficit conditions that triggers a suite of drought responses.Most likely the hormone is

A)ABA.
B)GA.
C)IAA.
D)2,4-D.

Question 59

If a short-day plant has a critical night length of 15 hours,then which of the following 24-hour cycles will prevent flowering?

A)8 hours light/16 hours dark
B)4 hours light/20 hours dark
C)6 hours light/2 hours dark/light flash/16 hours dark
D)8 hours light/8 hours dark/light flash/8 hours dark

Question 60

The transduction pathway that activates systemic acquired resistance in plants is initially signaled by

A)antisense RNA.
B)P_fr phytochrome.
C)salicylic acid.
D)abscisic acid.

Question 61

When plants exhibit generalized defense responses in organs distant from the infection site,this is termed

A)a hyperactive response.
B)systemic acquired resistance.
C)pleiotropy.
D)hyperplasia.

Question 62

This experiment suggests that the optimum amount of gibberellin in the experiment is approximately

A)zero.
B)0)01 μg/mL.
C)0)1 μg/mL.
D)1)0 μg/mL.

Question 63

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)increased activity of plasma membrane proton pumps.

Question 64

Which of the following plant hormones stimulates cell division and differentiation and apical dominance?

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

Question 65

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 66

The variety of leaf patterns in plants is due to

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

Question 67

This experiment suggests that the unknown amount of gibberellin in the experimental plant (B)is approximately

A)zero.
B)0)01 μg/mL.
C)0)1 μg/mL.
D)1)0 μg/mL.

Question 68

Which of the following is a long-day plant?

A)soybean
B)spinach
C)chrysanthemum
D)poinsettia

Question 69

When an arborist prunes a limb off a valuable tree,he or she usually paints 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 70

Which of the following synthetic auxin functions as a herbicide?

A)indolebutyric acid
B)indoleacetic acid
C)2,4-dichlorophenoxyacetic acid (2,4-D)
D)cytokinin

Question 71

In a tissue culture experiment,parenchyma tissue was used as a source to develop a new plant.However,the parenchyma tissue did not have enough hormones,so a group of undifferentiated cells,called callus,formed.Which one of the following could happen if the callus was supplemented with specific hormones?

A)Callus supplemented with auxin would produce shoot buds.
B)Callus supplemented with cytokinin would produce leaves.
C)Callus supplemented with auxin and cytokinin would produce root and shoot buds,respectively.
D)Callus supplemented with auxin and cytokinin would produce shoot buds and roots,respectively.

Question 72

In nature,poinsettias bloom in early March.Research has shown that the flowering process is triggered 3 months before blooming occurs.In order to make poinsettias bloom in December,florists change the length of the light/dark cycle in September.Given this information and clues,which of the following is a correct statement about poinsettias?

A)They are short-day plants.
B)They require a light period longer than some set minimum.
C)They require a shorter dark period than is available in September.
D)The dark period can be interrupted without affecting flowering.

Question 73

In an experiment,a plant physiologist has four groups of bananas of the same species.He exposes each of the four groups of bananas with the same concentration of auxins,gibberellins,abscisic acid,or ethylene.Which of these four groups of bananas ripen the fastest?

A)auxins
B)gibberellins
C)abscisic acid
D)ethylene

Question 74

Charles and Francis Darwin discovered that

A)red light is most effective in shoot phototropism.
B)auxin can pass through agar.
C)light destroys auxin.
D)light is perceived by the tips of coleoptiles.