Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

BIO 102 > Plant physiology and hormones > Flashcards

Plant physiology and hormones Flashcards

(106 cards)

Start Studying
1
Q

Which plant hormone is primarily responsible for cell elongation in plant shoots?

A

C. Auxin

Auxins, like indole-3-acetic acid, promote cell elongation especially in shoots via cell wall loosening.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

The first plant hormone to be discovered was identified through studies on phototropism. Which hormone was this?

A

C. Auxin

Auxin was isolated by Frits Went in 1928 using the Avena curvature experiment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

In his 1928 experiment with oat coleoptiles, what did Frits Went demonstrate?

A

B. A chemical from the coleoptile tip (auxin) can diffuse into agar and stimulate growth

Went’s experiment showed auxin diffuses from the coleoptile tip into agar, causing growth.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Charles and Francis Darwin’s experiments on grass coleoptiles led to which conclusion about phototropism?

A

C. The tip of the coleoptile detects light and produces a signal that causes bending

The tip senses light and produces auxin, which induces curvature.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Auxins in plants are primarily synthesized in the:

A

B. Shoot apical meristems and young leaves

Auxin is mainly produced in the shoot apex and young leaves.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Apical dominance in a plant is mainly maintained by:

A

B. Auxin produced by the apical meristem

Auxin suppresses lateral bud growth, maintaining apical dominance.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which synthetic auxin is widely used as a herbicide for broadleaf weeds?

A

B. 2,4-Dichlorophenoxyacetic acid (2,4-D)

2,4-D causes uncontrolled growth in broadleaf plants.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Which one of the following is a naturally occurring auxin in plants?

A

A. Indole-3-acetic acid (IAA)

IAA is the primary natural auxin; others like 2,4-D are synthetic.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The ‘acid growth hypothesis’ explains how auxin causes cell elongation by:

A

C. Promoting proton (H⁺) pumps that acidify the cell wall, loosening it for expansion

Auxin activates proton pumps, leading to cell wall loosening and elongation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Auxin transport in plant stems is characterized by being:

A

B. Polar (primarily from shoots toward roots) and requiring energy

Auxin moves in one direction, typically downward from the shoot tip.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which process is least associated with auxins?

A

C. Fruit ripening

Fruit ripening is primarily governed by ethylene, not auxin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

If the apical bud of a plant is removed, what is a likely effect on the plant?

A

A. Lateral buds will begin to grow more freely

Removing the apical bud eliminates apical dominance, allowing lateral buds to grow.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Applying auxin to an unpollinated flower can result in:

A

A. Fruit development without seeds (parthenocarpy)

External auxin can stimulate fruit development without fertilization.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

In plant tissue culture, a relatively high auxin to cytokinin ratio will most likely induce the formation of:

A

B. Roots

High auxin and low cytokinin favors root formation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens when auxin levels in a leaf or fruit drop?

A

A. Ethylene production increases and the organ abscises

Lower auxin leads to ethylene action, promoting abscission.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

The bending of plant stems toward a light source is primarily due to:

A

B. Lateral redistribution of auxin to the shaded side, causing more growth on that side

Higher auxin on the shaded side causes those cells to elongate more.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Gardeners often use ‘rooting powders’ when propagating plants from cuttings, which typically contain which hormone?

A

B. Auxin

Rooting powders contain auxins to stimulate root development.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

The Avena coleoptile curvature test is a classic bioassay used to detect which plant hormone?

A

C. Auxin

This bioassay measures auxin by observing curvature in response to its presence.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Which plant hormone is primarily responsible for dramatic stem elongation?

A

B. Gibberellin

Gibberellins promote stem elongation and can induce bolting in rosette plants.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

The ‘foolish seedling’ disease of rice is caused by overproduction of which hormone?

A

B. Gibberellin

The bakanae fungus secretes gibberellins, causing abnormal growth in rice seedlings.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Which of the following is not an effect normally associated with gibberellins?

A

C. Inducing fruit ripening in mature fruits

Gibberellins do not induce fruit ripening; this is primarily controlled by ethylene.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

A common agricultural use of gibberellin is to produce larger, elongated seedless grapes.

A

B. True

Gibberellin is used to stimulate cell expansion in seedless grape varieties.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Gibberellins have the opposite effect of which hormone in regulating seed dormancy and germination?

A

B. Abscisic acid

Abscisic acid induces dormancy, while gibberellins promote germination.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Semi-dwarf varieties of wheat and rice are short because they are deficient in or insensitive to which hormone?

A

C. Gibberellin

These varieties have mutations reducing gibberellin production or signaling.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
During germination of cereal grains, gibberellin released by the embryo causes the aleurone layer to:
A. Synthesize hydrolytic enzymes such as α-amylase to break down stored starch ## Footnote Gibberellins trigger enzyme production that converts starch to sugars for the growing seedling.
26
Which of these is a gibberellin hormone commonly used in plant physiology studies?
B. GA₃ (gibberellic acid) ## Footnote GA₃ is used in experiments and agriculture to stimulate growth.
27
Treatment with gibberellins can induce flowering in some plants that normally require specific conditions. For example, gibberellin can sometimes substitute for:
C. A cold period (vernalization) or long-day photoperiod in certain biennials ## Footnote Gibberellins can trigger flowering in plants needing prolonged cold or specific daylength.
28
What conditions are necessary for gibberellins to trigger flowering in certain plants?
A cold period (vernalization) or long-day photoperiod ## Footnote Gibberellins can induce flowering in biennial plants that typically require a cold period or specific daylength.
29
What is the likely outcome for a dwarf mutant plant that cannot synthesize gibberellins?
Remain very short unless gibberellin is applied externally ## Footnote A plant that cannot produce gibberellin will be very short with stunted internodes.
30
Which statement about gibberellins is correct?
They promote the mobilization of food reserves in seeds during germination ## Footnote Gibberellins break seed dormancy and stimulate germination by mobilizing nutrient reserves.
31
Where are gibberellins primarily synthesized in plants?
In young leaves, developing seeds, and shoot apices ## Footnote Gibberellins are produced in regions of active growth.
32
Gibberellins are chemically classified as:
Terpenoid compounds (diterpenes) ## Footnote Gibberellins are diterpenoid acids, with GA₃ being a tetracyclic diterpene.
33
Which plant hormone was discovered as the 'coconut milk factor'?
Cytokinin ## Footnote Cytokinins promote cell division and were initially identified from coconut milk.
34
A naturally occurring cytokinin found in plants is:
Zeatin ## Footnote Zeatin was first isolated from corn kernels and is a natural cytokinin.
35
In plants, cytokinins are primarily synthesized in the:
Root apical meristem (root tips) ## Footnote Cytokinins are synthesized mostly in root tips and transported to shoots.
36
What effect do cytokinins have on plant development?
Promotion of cell division and shoot formation ## Footnote Cytokinins stimulate cell division and promote shoot bud formation.
37
In tissue culture, a high cytokinin to auxin ratio tends to induce the development of:
Shoots (shoot buds) ## Footnote A higher cytokinin:auxin ratio favors shoot formation.
38
Which pair of hormones typically has opposing effects on apical dominance?
Auxin and Cytokinin ## Footnote Auxin inhibits lateral bud growth, while cytokinins promote it.
39
Which synthetic cytokinin is often used in plant tissue culture?
BAP (benzylaminopurine) ## Footnote BAP is commonly used to promote shoot proliferation in tissue culture.
40
What observation supports the role of cytokinins in delaying leaf senescence?
Leaves treated with cytokinin stay green longer than untreated leaves ## Footnote Cytokinins help preserve chlorophyll and protein content in leaves.
41
Which is not a typical effect or function of cytokinins in plants?
Initiation of adventitious root formation ## Footnote Cytokinins do not typically induce adventitious roots; auxins promote that process.
42
Cytokinin signaling in plant cells differs from auxin signaling in that cytokinin receptors are:
Histidine-kinase receptors located at the membrane (two-component system) ## Footnote Cytokinins are perceived by membrane-bound histidine kinase receptors.
43
Which statement is true about kinetin?
Kinetin was isolated as a breakdown product of DNA and is not naturally present in plants ## Footnote Kinetin mimics cytokinin effects but is not found in living plant tissues.
44
Cytokinins influence the distribution of nutrients in plants by:
Mobilizing nutrients toward areas of high cytokinin concentration ## Footnote Cytokinins attract nutrients to areas where they are present at higher levels.
45
Which hormone can help break the dormancy of lateral buds?
Cytokinin ## Footnote Cytokinins promote the growth of lateral buds when the apical bud is removed.
46
Which plant hormone is a gas that diffuses readily through plant tissues?
Ethylene ## Footnote Ethylene is unique among major plant hormones as it is gaseous.
47
The 'triple response' in etiolated seedlings is caused by which hormone?
Ethylene ## Footnote The triple response includes inhibition of stem elongation, thickening, and horizontal growth.
48
Which plant hormone is primarily responsible for the ripening of climacteric fruits?
Ethylene ## Footnote Ethylene triggers ripening, leading to softening and color changes in fruits.
49
A common commercial application of ethylene is:
To ripen harvested fruits such as bananas and tomatoes ## Footnote Ethylene is used to induce uniform ripening of fruits after harvest.
50
Ethylene production in plants is often stimulated by:
Auxin (high levels of IAA) ## Footnote High levels of auxin can induce ethylene synthesis in plant tissues.
51
Which of the following is not a typical effect of ethylene in plants?
Induction of seed dormancy ## Footnote Ethylene promotes fruit ripening and leaf abscission, but does not induce seed dormancy.
52
The immediate biosynthetic precursor of ethylene in plants is:
1-aminocyclopropane-1-carboxylic acid (ACC) ## Footnote ACC is the direct precursor that gets oxidatively cleaved to produce ethylene.
53
How is ethylene perceived by plant cells?
Via membrane-bound receptors (such as ETR1) mainly located on the endoplasmic reticulum ## Footnote Ethylene receptors function as part of a two-component-like system.
54
What is epinasty?
Downward curling or drooping of leaves ## Footnote Epinasty occurs due to greater growth on the upper side of the petiole than the lower side.
55
What is epinasty?
Downward curling or drooping of leaves ## Footnote Epinasty occurs due to greater growth on the upper side of the petiole than the lower side, often caused by ethylene accumulation.
56
Leaf and petal abscission is stimulated by ______ and can be delayed by high levels of ______ in the plant.
ethylene; auxin ## Footnote Ethylene promotes the formation of the abscission layer, while auxin delays abscission.
57
The purpose of reduced ethylene levels in storage facilities for fruits is to:
Prevent fruits from ripening too quickly during storage ## Footnote High CO₂ and low O₂ environments are used to delay ripening.
58
Flooding or waterlogged soil often leads to increased ethylene in roots, which can cause:
Formation of aerenchyma (air spaces) in roots ## Footnote Ethylene induces programmed cell death in root cortex cells, forming aerenchyma to help oxygen transport.
59
Which hormone is released by a ripe fruit and can induce other fruits to ripen faster?
Ethylene ## Footnote A ripening fruit emits ethylene, triggering nearby fruits to ripen quickly.
60
Ethylene can affect the sex expression of flowers in some monoecious plants by:
Promoting the formation of female flowers ## Footnote Ethylene treatments can increase female flowers for higher fruit yield.
61
Which plant hormone is often referred to as the 'stress hormone'?
Abscisic acid (ABA) ## Footnote ABA helps plants cope with drought and adverse conditions.
62
Abscisic acid (ABA) was initially discovered for its ability to:
Cause abscission of cotton bolls and induce bud dormancy ## Footnote It was named 'abscisic acid' after being identified as abscisin II and dormin.
63
What is the primary role of abscisic acid in seeds?
Inducing and maintaining seed dormancy ## Footnote ABA prevents premature germination and ensures seeds germinate under favorable conditions.
64
Which hormone triggers closing of stomata in plant leaves under water stress?
Abscisic acid ## Footnote ABA signals guard cells to close stomatal pores, conserving water.
65
Which of the following is not typically caused by abscisic acid?
Stimulation of extensive stem elongation growth spurts ## Footnote ABA generally inhibits growth; gibberellin is responsible for stem elongation.
66
A mutant plant that cannot produce abscisic acid would likely show which symptom?
Inability to close stomata, leading to wilting under drought ## Footnote ABA-deficient mutants cannot properly close stomata and will wilt rapidly.
67
What is the purpose of proteins synthesized due to abscisic acid accumulation in seeds?
They protect the seed from desiccation and other stresses ## Footnote These proteins help seeds survive extreme drying and stabilize cellular structures.
68
Which two hormones act antagonistically in seed germination versus dormancy?
Gibberellin and Abscisic acid ## Footnote Gibberellins promote germination, while abscisic acid enforces dormancy.
69
During a drought, which hormone's level would you expect to rise in leaves and roots?
Abscisic acid ## Footnote ABA signals the plant to conserve water by triggering stomatal closure.
70
Abscisic acid is chemically derived from:
Carotenoids ## Footnote ABA is produced via the cleavage of carotenoid precursors in chloroplasts.
71
Which scenario is most likely if a plant has very low abscisic acid levels?
Seeds germinate prematurely on the parent plant (vivipary) ## Footnote Low ABA levels prevent dormancy, leading to vivipary.
72
Which statement about abscisic acid (ABA) is correct?
ABA levels increase under water stress, leading to stomatal closure ## Footnote ABA inhibits growth and germination, helping conserve resources.
73
In buds of perennial plants, high levels of ABA during autumn maintain the buds in a ______ state.
dormant ## Footnote ABA induces dormancy and increases cold hardiness in buds.
74
Which of the following is a known effect of abscisic acid on plant development?
Promotion of root growth under mild stress ## Footnote ABA often slows shoot growth but can promote root growth to help the plant seek water.
75
Which of the following substances is not a plant hormone?
Insulin ## Footnote Insulin is an animal hormone, while auxin, ethylene, and abscisic acid are plant hormones.
76
One difference between plant hormones and animal hormones is that plant hormones:
Often act in the same tissues where they are produced and can diffuse to target cells ## Footnote Plant hormones can move locally, unlike animal hormones which are transported through a circulatory system.
77
Which of the following is a plant growth regulator that was not traditionally considered one of the five classic plant hormones?
Brassinosteroid ## Footnote Brassinosteroids were discovered later and are important growth regulators.
78
Florists treat cut flowers with silver thiosulfate to inhibit the action of which hormone?
Ethylene ## Footnote Silver thiosulfate blocks ethylene receptors, delaying flower senescence.
79
A plant that is genetically unable to produce carotenoids will likely be deficient in which hormone?
Abscisic acid (ABA) ## Footnote ABA synthesis relies on carotenoid precursors; a deficiency leads to problems with seed dormancy and stress responses.
80
If farmers anticipate a severe drought, they might spray a chemical that mimics which hormone to help plants conserve water?
Abscisic acid ## Footnote Mimicking ABA helps trigger drought responses in plants.
81
What hormone is synthesized from carotenoid precursors in chloroplasts?
Abscisic acid ## Footnote ABA is crucial for seed dormancy and drought responses.
82
Which hormone would farmers spray to help plants conserve water during drought?
Abscisic acid ## Footnote An ABA-like substance can cause stomata to close, aiding in drought defense.
83
What effect does auxin have compared to cytokinin on root versus shoot formation?
Auxin promotes adventitious root formation, while high cytokinin can inhibit rooting and instead promotes shoot formation ## Footnote This antagonism is utilized in tissue culture to control organ formation.
84
Which pair of plant hormones is known to have largely antagonistic effects?
Gibberellin and Abscisic acid ## Footnote Gibberellins promote growth, while abscisic acid promotes dormancy.
85
Which hormones work together to promote plant growth such as stem elongation?
Auxin and Gibberellin ## Footnote They synergistically stimulate growth processes.
86
What happens when the shoot tips are pinched off in plants?
Auxin levels drop, allowing higher cytokinin levels to promote lateral bud growth ## Footnote This leads to a bushier plant.
87
Which statement about hormone interactions is correct?
Auxin can stimulate ethylene production in tissues, leading to effects like leaf abscission and epinasty ## Footnote High auxin can induce ethylene synthesis, affecting leaf drop.
88
Which hormone is incorrectly paired with its use?
Cytokinin is widely used to induce malting (germination) in barley for beer production ## Footnote Gibberellins are the hormones that promote malting.
89
Who discovered auxin by demonstrating a growth-promoting chemical in coleoptile tips?
Frits Went ## Footnote His work in 1928 was pivotal in understanding plant growth hormones.
90
What feature do auxin and gibberellin share in their signal transduction pathways?
They both bind to soluble receptor proteins that lead to degradation of repressor proteins ## Footnote This mechanism is crucial for their growth-promoting effects.
91
Which two classes of plant hormones are perceived by similar types of membrane-bound receptors?
Cytokinins and Ethylene ## Footnote Both utilize histidine kinase receptors for signaling.
92
What is the intended effect of spraying naphthalene acetic acid (NAA) on fruit trees?
Prevent premature fruit drop before harvest ## Footnote This helps reduce yield loss.
93
What is the reason behind the misnomer of 'abscisic acid'?
It was thought to promote abscission, but ethylene is the primary abscission hormone ## Footnote ABA is now known primarily for its role in inducing dormancy.
94
What hormonal changes contribute to leaves changing color and falling off in deciduous trees during autumn?
An increase in ethylene and a decrease in auxin ## Footnote This hormonal shift triggers abscission and color change.
95
Which hormone is commonly added at high concentration in plant tissue culture to induce callus formation?
Auxin (e.g., high 2,4-D) ## Footnote High levels of auxin promote cell proliferation.
96
Which hormone produced in roots helps stimulate dormant buds to resume growth in spring?
Cytokinin ## Footnote Rising cytokinin levels signal buds to swell and open.
97
Which treatment could promote germination of light-sensitive lettuce seeds in the absence of light?
Applying gibberellin (GA) ## Footnote Gibberellins can mimic light signals necessary for germination.
98
What is the result of spraying ethylene-releasing compounds on fields before harvest?
Defoliation – leaves to drop for easier crop harvest ## Footnote This practice facilitates mechanical harvesting.
99
What is the intended effect of spraying a cytokinin on green leafy vegetables post-harvest?
To keep the leaves green and delay yellowing ## Footnote Cytokinins help maintain freshness and reduce spoilage.
100
Which plant hormone produced by the germinating barley grain is crucial for converting starches into sugars during malting?
Gibberellin ## Footnote It stimulates enzymes that break down starch.
101
Indole-3-acetic acid (IAA, an auxin) is biosynthetically derived from which amino acid?
Tryptophan ## Footnote This amino acid is the precursor for the primary natural auxin.
102
Dormant seeds or buds often have high ______ and low ______; to break dormancy, the balance shifts.
abscisic acid; gibberellin ## Footnote High ABA enforces dormancy, while gibberellin promotes growth.
103
Dormant seeds or buds often have high ______ and low ______; to break dormancy, the balance shifts.
abscisic acid; gibberellin ## Footnote Dormant seeds and buds usually contain high abscisic acid (ABA, enforcing dormancy) and low gibberellin. To break dormancy, ABA levels drop and gibberellin levels rise, promoting growth.
104
The 'Never-ripe' mutation in tomato affects the plant’s sensitivity to which hormone?
Ethylene ## Footnote The 'Never-ripe' mutant in tomato has a defect in an ethylene receptor, making the plant insensitive to ethylene, leading to fruits that do not ripen normally.
105
At one time, abscisic acid was also known by which name due to its role in inducing dormancy?
Dormin ## Footnote Abscisic acid was discovered as a bud dormancy-inducing factor and was called 'dormin' by one research group.
106
True or False: The other amino acids listed are direct precursors of IAA.
False ## Footnote Only certain amino acids are precursors of IAA; the others listed are not.

BIO 102 (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions