Question 1

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

Accepted Answer

Phototropin is a blue-light receptor protein found in plants that is involved in the response to light, particularly in regulating phototropism (the bending of plants towards light) and chloroplast movement. It is not a type of phytochrome, hormone receptor, hormone or transcription factor.

Question 2

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.

Accepted Answer

The binding of cytokinins to its receptor protein leads to protein kinase activity at the cytoplasmic end of the receptor, which then activates downstream effectors. This is a classic example of a receptor tyrosine kinase pathway.

Question 3

All of the following are plant hormones except
A) abscisic acid.
B) brassinosteroids.
C) cytokinins.
D) gibberellins.
E) phytochrome.

Accepted Answer

Phytochrome is not a plant hormone, but rather a protein pigment that regulates various plant responses to light such as photomorphogenesis and photoperiodism.

Question 4

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

Accepted Answer

Red light is known to promote seed germination in many plant species by activating phytochromes. Since traditional methods like hormone treatments and temperature variations did not work, red light may be a viable option to induce germination in this desert shrub.

Question 5

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

Accepted Answer

The production of auxin in response to light involves phototropin. Phototropin is a blue light receptor found in plants. When activated by blue light, phototropin triggers the production and transport of auxin, leading to plant growth towards the light source (phototropism). Zeaxanthin and phytochrome P_r are not directly involved in the production of auxin in response to light, and the exact mechanism is not fully understood, but it does involve phototropin.

Question 6

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

Accepted Answer

Commercial preparations of abscisic acid can be applied to cereal grains in order to prevent seed germination.

Question 7

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.

Accepted Answer

Phytochrome can be converted into two different forms, Pr and Pfr, depending on the specific wavelengths of light that it absorbs. This allows plants to detect changes in photoperiod, as the ratio of Pr to Pfr changes depending on the duration of light and darkness.

Question 8

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.

Accepted Answer

The answer of Which statement about phytochrome P_r is true? A)...

Question 9

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.

Accepted Answer

The answer of The physiologically active form of phytochrome
A) is...

Question 10

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

Accepted Answer

A low auxin-to-cytokinin ratio promotes bushiness in plants by encouraging lateral bud growth and reducing apical dominance.

Question 11

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

Accepted Answer

Ethylene is a plant hormone that triggers the ripening process in fruit, including lemons. The apple releases ethylene gas, which speeds up the natural ripening process of the lemon.

Question 12

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.

Accepted Answer

Silver thiosulfate is used to inhibit the action of ethylene, which is responsible for causing petals to turn brown and fall off.

Question 13

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

Accepted Answer

Ethylene has been shown to promote leaf senescence in tobacco, while auxin has been shown to delay it. Therefore, applying ethylene would promote senescence and applying auxin would delay it.

Question 14

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

Accepted Answer

Ethylene does not affect the opening of the eudicot apical hook.

Question 15

Which plant hormone is a gas?
A) Cytokinins
B) Abscisic acid
C) Gibberellins
D) Auxin
E) Ethylene

Accepted Answer

Ethylene is the only plant hormone that exists in a gaseous state. It is responsible for a variety of physiological processes, including fruit ripening, abscission, and the response to stress.

Question 16

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.

Accepted Answer

Ethylene is a gas hormone, which makes it unique among other plant hormones.

Question 17

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

Accepted Answer

Cytokinin signal transduction begins with cytokinin binding to its receptor, which then initiates cytoplasmic steps, leading to the activation of transcription factors.

Question 18

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

Accepted Answer

This is because phytochromes, the plant photoreceptors responsible for detecting light, are most sensitive to red light. When red light is absorbed by the phytochromes, they undergo a conformational change that triggers a signaling cascade leading to germination. Far-red light, on the other hand, can actually inhibit germination by reversing the conformational change induced by red light. Green light is not absorbed well by plant pigments and therefore has little effect on germination. The initiation of photosynthesis is not directly related to seed germination.

Question 19

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

Accepted Answer

Ethylene is responsible for triggering the process of abscission, which causes leaves to fall off in the fall. If the plant lacks the receptor for ethylene, it would be unable to undergo abscission in the fall. Therefore, option D is the best choice. Option A is not related to ethylene receptor, option B is related to chlorophyll rather than ethylene, and option C is not a known compensatory response to the lack of ethylene receptor.

Question 20

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.

Accepted Answer

The answer of Shortly after sundown after a long sunny...

Quiz 26: Plant Growth and Development

Phototropin is a

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

All of the following are plant hormones except

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?

The production of auxin in response to light involves

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

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

Which statement about phytochrome P_r is true?

The physiologically active form of phytochrome

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

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?

Florists use silver thiosulfate to

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

Which process is not affected by ethylene?

Which plant hormone is a gas?

Unlike other plant hormones,ethylene

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

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

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

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