Chapter 27: Regulating Growth and Development: The Plant Hormones
Multiple-Choice Questions
1.Introduction; pp. 638–639; easy; ans: e
All plant hormones:
a.are equally effective in free and bound forms.
b.act in the tissues where they are produced.
c.are stimulatory.
d.are active in large quantities.
e.communicate information.
2.Introduction; p. 639; easy; ans: c
______have recently been ranked along with the “classic five” as a major class of plant hormone.
a.Systemins
b.Florigens
c.Brassinosteroids
d.Salicylic acids
e.Jasmonates
3.Introduction; p. 639; easy; ans: d
Which of the following is a phenolic compound with a structure similar to aspirin?
a.systemin
b.florigen
c.brassinosteroids
d.salicylic acids
e.jasmonic acid
4.Introduction; p. 639; difficult; ans: a
______activates the biosynthesis of ______, which then activates the genes that encode protease inhibitors.
a.Systemin; jasmonic acid
b.Jasmonic acid; auxin
c.Brassinosteroid; systemin
d.Salicylic acid; jasmonic acid
e.Systemin brassinosteroids
5.Auxins; p. 639; easy; ans: b
If a coleoptile tip is covered with a blackened glass tube then illuminated from the side, the coleoptile will:
a.die.
b.not bend.
c.bend toward the light.
d.bend away from the light.
e.bend at right angles to the light.
6.Auxins; p. 639; easy; ans: c
______is very similar to the amino acid tryptophan.
a.Gibberellin
b.Cytokinin
c.Indoleacetic acid
d.Abscisic acid
e.Ethylene
7.Auxins; p. 641; moderate; ans: e
Polar transport is ______in stems, ______in leaves, and ______in roots.
a. acropetal; acropetal; acropetal
b.basipetal; basipetal; basipetal
c.acropetal; acropetal; basipetal
d.basipetal; acropetal; acropetal
e.basipetal; basipetal; acropetal
8.Auxins; p. 641; difficult; ans: c
In stems, polar auxin transport occurs mainly in the:
a.vessels only.
b.sieve tubes only.
c.vascular parenchyma cells only.
d.vessels and sieve tubes.
e.vessels and parenchyma cells.
9.Auxins; p. 641; difficult; ans: b
A PIN protein:
a.is an auxin influx carrier.
b.is an auxin efflux carrier.
c.catalyzes the conversion of auxin to tryptophan.
d.catalyzes the conversion of auxin to indole.
e.is a synthetic auxin.
10.Auxins; p. 642; difficult; ans: a
Which of the following statements concerning the role of auxin in developing leaves of Arabidopsis is FALSE?
a.Auxin is produced first at the leaf base and later at the tip.
b.Auxin stimulates the differentiation of vascular tissue.
c.Auxin induces the formation of lateral veins.
d.Auxin is produced by cells that will differentiate into hydathodes.
e.Auxin induces the formation of the midvein.
11.Auxins; pp. 642–643; difficult; ans: c
If wounding causes the destruction of vascular tissues in an herbaceous eudicot stem:
a.replacement vascular tissues will not form under any conditions.
b.replacement vascular tissues will form if IAA is added to the stem just below the wound.
c.replacement vascular tissues will form if the leaves and buds above the wound are intact.
d.water will be transported in pith cells instead of in xylem.
e.food will be transported in pith cells instead of in phloem.
12.Auxins; p. 643; easy; ans: a
In apical dominance, the apical bud:
a.inhibits the growth of lateral buds.
b.stimulates the growth of lateral buds.
c.stimulates the upward growth of the stem.
d.stimulates the growth of leaves.
e.inhibits the downward growth of the root.
13.Auxins; p. 644; difficult; ans: c
Which of the following statements concerning strigolactone is FALSE?
a.It is a terpenoid derived from carotenoids.
b.It stimulates bud growth.
c.It is present in root exudates.
d.It promotes the formation of mycorrhizae.
e.It stimulates seed germination of root-parasitic plants.
14.Auxins; p. 644; moderate; ans: b
Which of the following statements about fruit development is FALSE?
a.A parthenocarpic fruit lacks seeds.
b.A parthenocarpic fruit lacks ovules.
c.Applications of auxin can stimulate carpels to develop into a fruit.
d.Removal of seeds from a developing fruit results in reduced fruit growth.
e.Application of auxin to a deseeded receptacle stimulates fruit growth.
15.Auxins; p. 644; moderate; ans: e
Which of the following statements about 2,4-D is FALSE?
a.It is a synthetic auxin.
b.It is used as an herbicide.
c.It is not broken down in plants as readily as IAA.
d.It is absorbed more readily than IAA
e.It kills grasses more readily than broad-leaf weeds.
.
16.Cytokinins; p. 645; easy; ans: a
Folke Skoog and his colleagues found that ______stimulated cells of tobacco to divide in culture.
a.coconut milk
b.a sugar
c.a salt
d.a vitamin
e.auxin
17.Cytokinins; p. 645; moderate; ans: c
Which of the following statements about cytokinins is FALSE?
a.They stimulate cell division.
b.They are present in bleeding sap.
c.Kinetin is a naturally occurring cytokinin.
d.They are found primarily in actively dividing tissues and in root tips.
e.The most active naturally occurring cytokinin is zeatin.
18.Cytokinins; p. 646; moderate; ans: b
When tobacco pith callus is treated with higher concentrations of auxin than kinetin, ______is(are) formed.
a.more callus
b.roots
c.buds
d.leaves
e.vascular tissue
19.Cytokinins; p. 646; moderate; ans: a
In roots of Arabidopsis, cytokinin ______the initiation of lateral roots by preventing the establishment of a(n) ______gradient.
a.inhibits; auxin
b.inhibits; gibberellin
c.stimulates; auxin
d.stimulates; gibberellin
e.stimulates; ethylene
20.Cytokinins; p. 646; difficult; ans: d
In studies of leaf senescence, when an excised leaf containing radioactive amino acids is spotted with a kinetin-containing solution, the spot:
a.turns yellow and becomes nonradioactive.
b.turns yellow and becomes more radioactive.
c.remains green and becomes nonradioactive.
d.remains green and becomes more radioactive.
e.turns brown and becomes nonradioactive.
21.Cytokinins; p. 646-647; easy; ans: d
Cytokinins are synthesized in ____ and transported from there to all other parts of the plant.
a.stems
b.shoot apical meristems
c.leaves
d.roots
e.fruits
22.Ethylene; p. 647; moderate; ans: b
Which of the following statements about ethylene is FALSE?
a.The final step in its synthesis in plants is catalyzed by enzymes on the tonoplast.
b.Its synthesis in plants begins with the amino acid tryptophan.
c.It exerts an influence on many aspects of plant growth and development.
d.It is the active component of illuminating gas that affects plant development.
e. It has the formula H2C=CH2.
23.Ethylene; p. 647; difficult; ans: c
In etiolated pea seedlings, ethylene causes ______longitudinal growth, ______radial expansion of epicotyls, and ______growth of epicotyls.
a.increased; increased; horizontal
b.increased; decreased; horizontal
c.decreased; increased; horizontal
d.decreased; increased; angular
e.increased; decreased; angular
24.Ethylene; p. 648; easy; ans: d
The climacteric is the phase in which fruits undergo a(n):
a.decrease in photosynthesis.
b.decrease in respiration.
c.increase in photosynthesis.
d.increase in respiration.
e.increase in pectin synthesis.
25.Abscisic Acid; pp. 649–650; moderate; ans: d
Which of the following statements about abscisic acid is FALSE?
a.It has no direct role in abscission.
b.It induces the closing of stomata.
c.It prevents premature seed germination.
d.It inhibits the production of seed storage proteins.
e.It is produced during water stress.
26.Gibberellins; p. 650; easy; ans: e
Dwarf mutant plants are short because they:
a.synthesize too much gibberellin.
b.synthesize too much abscisic acid.
c.cannot synthesize ethylene.
d.cannot synthesize auxin.
e.cannot synthesize gibberellin.
27.Gibberellins; p. 651; moderate; ans: b
In germinating barley seeds, the ______releases gibberellins, which then diffuse to the ______where they stimulate the synthesis of hydrolytic enzymes.
a.endosperm; aleurone layer
b.embryo; aleurone layer
c.aleurone layer; embryo
d.aleurone layer; endosperm
e.embryo; seed coat
28.Gibberellins; pp. 651–652; moderate; ans: c
Which of the following statements about gibberellins is FALSE?
a.They induce bolting in long-day plants.
b.They induce early flowering in biennials.
c.They cause rosette formation in cabbages and carrots.
d.They cause development of parthenocarpic apples and currants.
e.They are used in the commercial production of seedless grapes.
29.Brassinosteroids; p. 652; easy; ans: a
The most widespread and active brassinosteroid is:
a.brassinolide.
b.24-epibrassinolide.
c.S-adenosylmethionine.
d.strigolactone.
e.castasterone.
30.Brassinosteroids; pp. 652-653; easy; ans: e
Which of the following statements concerning endogenous brassinosteroids is FALSE?
a.They are found in virtually every part of the plant.
b.They are synthesized from castasterone.
c.They are essential for tracheary element differentiation.
d.They are required for normal plant growth.
e.They are transported from root to shoot in the xylem.
31.The Molecular Basis of Hormone Action; p. 655; moderate; ans: c
In isolated barley aleurone cells, treatment with GA causes the levels of α-amylase to ______, and treatment with ABA causes the levels to ______.
a.increase; remain unchanged
b.decrease; remain unchanged
c.increase; decrease
d.decrease; increase
e.increase; increase
32.The Molecular Basis of Hormone Action; p. 655; moderate; ans: b
Cell wall extensibility, and thus cell expansion, is increased by ______but decreased by ______.
a.auxin and ethylene; GA and ABA
b.auxin and GA; ABA and ethylene
c.auxin and ABA; GA and ethylene
d.ABA and ethylene; auxin and GA
e.ABA and GA; auxin and ethylene
33.The Molecular Basis of Hormone Action; p. 655; difficult; ans: d
In the acid-growth hypothesis of cell wall extensibility, which of the following events occurs FIRST?
a.Expansins disrupt hydrogen bonds.
b.Protons are pumped into the cell wall.
c.Specific genes are activated.
d.A proton-pumping enzyme is activated.
e.Cross-links between noncellulosic polysaccharides are broken.
34.The Molecular Basis of Hormone Action; p. 655; moderate; ans: e
If cell wall microfibrils are oriented transversely, the cell normally expands:
a.in all directions.
b.at an oblique angle.
c.first laterally and then longitudinally.
d.laterally.
e.longitudinally.
35.The Molecular Basis of Hormone Action; pp. 655-656; difficult; ans: c
Gibberellins promote a ______orientation of the microtubules underlying the plasma membrane, and ethylene promotes a ______orientation.
a.random; longitudinal
b.transverse; random
c.transverse; longitudinal
d.longitudinal; transverse
e.longitudinal; random
36.The Molecular Basis of Hormone Action; p. 656; moderate; ans: a
In Arabidopsis, the ethylene receptor is located in the:
a.endoplasmic reticulum.
b.plasma membrane.
c.Golgi apparatus.
d.chloroplast.
e.nucleus.
37.The Molecular Basis of Hormone Action; p. 656; difficult; ans: b
In the ethylene signaling pathway in Arabidopsis, when ethylene is absent, then ____ is active.
a.EIN2
b.CTR1
c.EIN3
d.ERF1
e.Cu
38.The Molecular Basis of Hormone Action; p. 656; difficult; ans: c
In the ethylene signaling pathway in Arabidopsis, when the EIN2 protein is activated which of the following happens next?
a.ETR1 undergoes a conformational change.
b.CTR1 is activated.
c.the ethylene signal is transmitted into the nucleus.
d.a transcription factor is activated.
e.genes are activated.
39.The Molecular Basis of Hormone Action; p. 656; moderate; ans: e
The receptors for both auxin and gibberellin are located in the:
a.endoplasmic reticulum.
b.plasma membrane.
c.Golgi apparatus.
d.chloroplast.
e.nucleus.
40.The Molecular Basis of Hormone Action; p. 656; moderate; ans: b
The brassinosteroid receptor differs from the receptors for auxin, gibberellin, ethylene and cytokinins in that the brassinosteroid receptor:
a.is located entirely in the endoplasmic reticulum.
b.has an extracellular region, a transmembrane region, and a cytoplasmic region.
c.is located entirely in the cytoplasm.
d.does not initiate a signaling cascade.
e.binds directly with genes in the nucleus.
41.The Molecular Basis of Hormone Action; p. 657; moderate; ans: d
Which of the following statements about second messengers is FALSE?
a.They amplify the signal produced by a hormone.
b.They contribute to the diversity of responses to a hormone.
c.They transfer information from the hormone-receptor complex to the target protein.
d.An example is protein kinase.
e.An example is calcium ion.
42.The Molecular Basis of Hormone Action; p. 658; difficult; ans: a
In the ABA-induced closing of stomata, the following ion fluxes occur across guard cell plasma membranes: first calcium ions flow ______, then anions flow ______, and finally potassium ions flow ______.
a.in; out; out
b.in; in; in
c.out; in; out
d.out; out; in
e.out; out; out
True-False Questions
1.Introduction; p. 639; easy; ans: F
Plant hormones usually act alone and only occasionally “cross-talk.”
2.Introduction; p. 639; moderate; ans: T
Salicylic acid regulates thermogenesis in members of the arum family.
3.Introduction; p. 639; easy; ans: F
Jasmonic acid has a structure similar to aspirin.
4.Auxins; p. 641 ; easy; ans: T
Auxin is the only plant hormone known to be transported in a polar manner.
5.Auxins; p. 641; moderate; ans: F
In roots, a substance transported in a basipetal direction is transported toward the root tip.
6.Auxins; p. 641; moderate; ans: T
The transport of auxin can be nonpolar as well as polar.
7.Auxins; p. 643; easy; ans: F
If you cut the tip off a bean plant, the lateral buds will stop developing.
8.Auxins; p. 644; difficult; ans: T
Recent evidence indicates that auxin does not directly inhibit the growth of lateral buds.
9.Auxins; p. 644; easy; ans: F
The weed killer 2,4-D is a synthetic cytokinin.
10.Cytokinins; p. 645; moderate; ans: F
Application of cytokinin inhibits the growth of lateral buds.
11.Cytokinins; p. 646; moderate; ans: T
An excised leaf floated in a kinetin solution will remain green longer than a leaf floated in water.
12.Cytokinins; pp. 646-647; moderate; ans: T
Cytokinins are synthesized in roots and transported in the xylem to other parts of the plant.
13.Ethylene; p. 647; easy; ans: T
Ethylene stimulates internodal elongation of rice plants that are submerged during monsoon flooding.
14.Ethylene; p. 648; easy; ans: T
In climacteric fruits, there is a large increase in cellular respiration during ripening.
15.Abscisic Acid; p. 649; moderate; ans: F
One of the principal roles of abscisic acid is in leaf, flower, and fruit abscission.
16.Gibberellins; p. 650; easy; ans: T
Rice plants grow rapidly and become spindly due to the presence of gibberellic acid produced by a fungus.
17.Gibberellins; p. 652; easy; ans: T
Gibberellins promote fruit development in some species in which auxin does not.
18.Brassinosteroids; p. 653; moderate; ans: T
Mutants of Arabidopsis that lack brassinosteroids have leaves that are smaller and have fewer cells than the wild-type.
19.Brassinosteroids; p. 653; difficult; ans: T
Based on the results of experiments with cultured mesophyll cells of Zinnia elegans, you would predict that if brassinosteroids were excluded from the culture medium, no tracheary elements would be formed.
20.The Molecular Basis of Hormone Action; pp. 653-654; easy; ans: F
A cortical cell and a mesophyll cell from the same plant most likely have different genes in their nuclei.
21.The Molecular Basis of Hormone Action; p. 655; moderate; ans: T
Expansins are proteins that disrupt hydrogen bonds between cell wall polysaccharides.
22.The Molecular Basis of Hormone Action; p. 656; moderate; ans: F
In Arabidopsis, the ethylene receptor is located in the plasma membrane.
23.The Molecular Basis of Hormone Action; p. 657; moderate; ans: F
Second messengers do not cross the plasma membrane and enter the cytosol.
24.The Molecular Basis of Hormone Action; p. 658; moderate; ans: F
When potassium ions move out of guard cells, water follows by osmosis and the stomatal pore opens.
Essay Questions
1.Introduction; pp. 638–639; moderate
What are some basic characteristics of hormones? Name the “classic five” plant hormones as well as the hormone that now becomes #6. Then, give four examples of chemical regulators that do not fit into these groups.
2.Auxins; pp. 641; moderate
What is meant by “polar transport”? Describe the mechanism of the polar transport of auxin in plants.
3.Auxins; pp. 642–645; difficult
Describe the effects of applied auxin on (a) the differentiation of vascular tissues, (b) the growth of lateral buds, (c) the formation of adventitious roots, (d) the growth of fruits, and (e) the growth of weeds.
4.Cytokinins; pp. 646–647; moderate
Discuss the effects of kinetin on leaf senescence in excised leaves.
5.Ethylene; p. 647; easy
Explain what is meant by the “triple response.” In what ways is it adaptive?
6.Ethylene; pp. 647-649; moderate
Describe the effects of applied ethylene on (a) fruit ripening, (b) abscission, and (c) sex expression in cucurbits.
7.Abscisic Acid; pp. 649–650; difficult
List some of the effects of ABA. Use these examples to show that ABA can be classed as an inhibitor in some respects and a promoter in others.
8.Gibberellins; p. 650; moderate
Discuss the role of GA in stem growth using results obtained with GA-deficient mutants.
9.Gibberellins; p. 651; moderate
Describe the mechanism by which gibberellins stimulate the germination of barley seeds.
10.Brassinosteroids; p. 653; moderate
Explain the evidence for the effect of brassinosteroids on (a) normal plant growth and (b) the differentiation of tracheary elements.
11.The Molecular Basis of Hormone Action; pp. 655-656; moderate
Discuss the ways in which plant hormones affect the shape of cells.
12.The Molecular Basis of Hormone Action; p. 656; difficult
Explain how receptor proteins and signal transduction pathways are involved in the mechanism of action of hormones.
13.The Molecular Basis of Hormone Action; p. 657; moderate
Discuss the functioning of second messengers. What do you think “first messengers” are?
14.The Molecular Basis of Hormone Action; pp. 657–658; difficult
Discuss the mechanism by which ABA regulates the opening of stomata.