Question 1

Auxins (IAA)  in plants are known to affect all of the following processes except

Accepted Answer

A)   geotropism of shoots.
B)   maintenance of seed dormancy.
C)   phototropism of shoots.
D)   inhibition of lateral buds.
E)   fruit development.

Question 2

Which of the following conclusions is supported by the research of both Went and Charles and Francis Darwin on shoot responses to light?

Accepted Answer

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.
E)   Light stimulates the synthesis of a plant hormone that responds to light.

Question 3

A long-day plant will flower

Accepted Answer

A)   in the late fall.
B)   when the night is shorter than a critical value.
C)   only under artificial light in the summer.
D)   during short days with proper fertilization.
E)   regardless of the photoperiod imposed.

Question 4

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

Accepted Answer

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

Question 5

A long-day plant will flower if

Accepted Answer

A)   the duration of continuous light exceeds a critical length.
B)   the duration of continuous light is less than a critical length.
C)   the duration of continuous darkness exceeds a critical length.
D)   the duration of continuous darkness is less than a critical length.
E)   it is kept in continuous far-red light.

Question 6

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

Accepted Answer

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.
E)   starch and downward movement are necessary for thigmotropism.

Question 7

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

Accepted Answer

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.
E)   will still flower if ethylene is administered.

Question 8

Which of the following statements is correct with regard to a "circadian rhythm" in plants?

Accepted Answer

A)   It may have the same signal transduction pathway in all organisms.
B)   Once set, it cannot be changed.
C)   It works independently of photoperiodic responses.
D)   Once set, it is independent of external signals.
E)   It can be changed to a longer or shorter period by altering the light quality.

Question 9

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

Accepted Answer

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.
E)   actively absorb salts from the seawater.

Question 10

The detector of light during de-etiolation (greening)  of a tomato plant is (are)

Accepted Answer

A)   carotenoids.
B)   xanthophylls.
C)   phytochrome.
D)   chlorophyll.
E)   auxin.

Question 11

Plant hormonal regulation differs from animal hormonal regulation in that

Accepted Answer

A)   there are no dedicated hormone-producing organs in plants as there are in animals.
B)   all production of hormones is local in plants with little long-distance transport.
C)   plants do not exhibit feedback mechanisms like animals.
D)   only animal hormone concentrations are developmentally regulated.
E)   only animal hormones may have either external or internal receptors.

Question 12

How does indoleacetic acid affect fruit development?

Accepted Answer

A)   by preventing pollination
B)   by inhibiting formation of the ovule
C)   by promoting gene expression in cambial tissue
D)   by promoting rapid growth of the ovary
E)   by inducing the formation of brassinosteroids

Question 13

What does a short-day plant require in order to flower?

Accepted Answer

A)   a burst of red light in the middle of the night
B)   a burst of far-red light in the middle of the night
C)   a day that is longer than a certain length
D)   a night that is longer than a certain length
E)   a higher ratio of Pr to Pfr

Question 14

Experiments on the positive phototropic response of plants indicate that

Accepted Answer

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.
E)   auxin is only of secondary importance in the process.

Question 15

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?

Accepted Answer

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

Question 16

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

Accepted Answer

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.
E)   are correlated with moisture availability.

Question 17

Charles and Francis Darwin discovered that

Accepted Answer

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

Question 18

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?

Accepted Answer

A)   CO2
B)   cytokinins
C)   ethylene
D)   auxin
E)   gibberellic acids

Question 19

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

Accepted Answer

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

Question 20

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

Accepted Answer

A)   cause increased flower production.
B)   have no effect upon flowering.
C)   inhibit flowering.
D)   stimulate flowering.
E)   convert florigen to the active form.

Exam 31: Plant Responses to Internal and External Signals

A long-day plant will flower if

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Experiments on the positive phototropic response of plants indicate that

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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?

Correct AnswerverifiedShow Answer

Which of the following conclusions is supported by the research of both Went and Charles and Francis Darwin on shoot responses to light?

Correct AnswerverifiedShow Answer

How does indoleacetic acid affect fruit development?

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

The detector of light during de-etiolation (greening) of a tomato plant is (are)

Correct AnswerverifiedShow Answer

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?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Which of the following statements is correct with regard to a "circadian rhythm" in plants?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Charles and Francis Darwin discovered that

Correct AnswerverifiedShow Answer

Auxins (IAA) in plants are known to affect all of the following processes except

Correct AnswerverifiedShow Answer

Plant hormonal regulation differs from animal hormonal regulation in that

Correct AnswerverifiedShow Answer

A long-day plant will flower

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

What does a short-day plant require in order to flower?

Correct AnswerverifiedShow Answer

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