Plant Hormones Questions and Answers pdf

Plant hormones

Plant Hormones, also known as phytohormones, are organic substances produced by plants and help in regulating the growth and development of the plant. Plant synthesis a variety of plant hormones including:

1. Auxins
2. Gibberellins
3. Cytokinins
4. Abscisic acid
5. Ethylene

Various functions performed by plant hormones

Let’s have a brief overview of the functions and commercial applications of the above-mentioned plant hormones before solving plant hormones questions and answers.

Note: See Table 1 below to find out the definitions of some common terms used in botany.

1. Auxins (IAA)

Auxins are a class of plant hormones that are indole acetic acids in nature. They carry out various functions in the plant such as:

1. Stimulate cell enlargement in the region behind the apex and cambium.
2. Low concentration stimulates root growth and vice versa.
3. Promote root growth from cutting and calluses.
4. Stimulate bud initiation in shoots.
5. Stimulate apical dominance
6. Promote fruit growth.
7. Delay fruit drop
8. Sometimes induce parthenocarpy.
9. Delay leaf senescence in a few species.
10. Inhibit abscission.

Commercial applications

Various synthetic IAA compounds are available in the market which is cheap and very effective. Some of the commercial applications of auxins are:

1. Synthetic auxins i.e., Naphthalene acetic acid (NAA) and Indole propionic acid are used to promote parthenocarpy and fruiting in plants.
2. The 2,4 dichloro phenoxy acetic acid (2,4 D) is used as a selective weed killer to eradicate broad-leaved species. It is also used to inhibit potato sprouting and dropping of fruit prematurely.

Video lesson on auxins

2. Gibberellins (GA)

Gibberellins (Gibberellic acid) are plant hormones that perform various functions in plants including:

1. Stimulate cell enlargement by enhancing the effect of auxins on cell division in meristematic tissues of apical meristem and cambium.
2. Stimulate bolting of some rosette plants.
3. Induce parthenocarpy.
4. Promote bud initiation in shoots of chrysanthemum callus.
5. Promote fruit growth.
6. Break seed and bud dormancy.
7. Stimulate flowering in long-day plants.
8. Delay leaf senescence in a few species.

Commercial applications

The commercial applications include:

1. A spray of Gibberellic acid (GA) stimulates fruiting in pears and tangerines. It is used to produce seedless fruit by parthenocarpy and also used to increase berry size (e.g., in grapes).
2. The plant hormone GA3 is used in the brewing industry to enhance α-amylase production in barley which in turn promotes the malting process.
3. The spray of GA is used to delay the ripening process and to improve the storage life of bananas and grapes.

Video lesson on gibberellin

3. Cytokinin

They perform various functions in plants such as:

1. Stimulate cell division in apical meristem and cambium to increase stem growth.
2. Stimulate lateral root and bud growth.
3. Promote leaf and fruit growth.
4. Seldom induce parthenocarpy.
5. Break bud dormancy.
6. Promote the opening of stomata.
7. Delay leaf senescence.

Commercial Applications

Commercial applications include:

1. The spray of cytokinins keeps the leaves of cabbage and lettuce fresh and green.
2. Keep flowers fresh.
3. Used to break the dormancy of some seeds.

Video lesson on cytokinin

4. Abscisic Acid (ABA)

The functions performed by ABA in plants include:

1. Inhibit root and stem growth, particularly during physiological stress e.g., waterlogging and drought.
2. Stimulate seed and bud dormancy.
3. Promote flowering in short-day plants.
4. Occasionally stimulate leaf senescence.
5. Stimulate stomata closing during water stress i.e., wilting.

Commercial Applications

Sprayed on tree crops to regulate fruit drop at the end of the season.

Video lesson on abscisic acid

5. Ethene or Ethylene

They perform various functions in plants such as:

1. Prevent stem growth, particularly during physiological stress.
2. Stop root growth
3. Break bud dormancy.
4. Stimulate flowering in pineapple.
5. Promote ripening of fruits.
6. Causes leaf abscission

Commercial applications

Some of the commercial applications of ethene are:

1. Stimulate flowering in pineapple.
2. Promote ripening of tomatoes and citrus fruits.

Video lesson on ethylene

Table 1. Definitions of common botany terms.

Terms	Definition
Parthenocarpy	Development of fruit without fusion of male and female gametes (fertilization).
Senescence	Biological aging or deterioration of functional characterization in living organisms.
Abscission	Normal separation or shedding of a plant part e.g., leaf.
Bolting	Premature growth of flower stalks in vegetable plants.
Malting	Process of steeping, germinating, and drying barley grains to convert them into malt. The malt is mainly used for brewing or whisky making.
Ripening	Process in fruits that causes them to become sweeter, less green, soft, and palatable.
Drought	Prolonged dry period.
Waterlogging	Excess water in the root zone is accompanied by anaerobic conditions.
Dormancy	Process in which plant meristems become mostly inactive to withstand harsh environmental conditions

Plant hormones questions and answers pdf

Plant hormones questions and answers will be useful in the preparation of many exams but also provide in-depth knowledge of their effect on plant growth and development. Some important questions and answers are below:

A. Selective the correct answer.

1. …….. promote root growth from cutting and calluses.

A. Cytokinin
B. Gybberellin
C. Auxin
D. Ethylene
Ans. C

2. Which is the most commonly used synthetic auxin?

A. IAA
B. NAA
C. GA
D. GA3
Ans. B

3. Which hormone promotes bolting in some rosette plants?

A. IAA
B. NAA
C. ABA
D. GA
Ans. D

4. Which of the following plant hormone is found in gaseous form?

A. Florigens
B. Abscisic Acid
C. Ethylene
D. Auxin
Ans. C

5. Ethene induces flowering in ……….

A. Rubber plant
B. Pineapple
C. Rosette plant
D. None of the above
Ans. B

6. ……. Causes delay in senescence

A. Auxins
B. Ascorbic acid
C. Cytokinins
D. Gibberellins
Ans. C

7. Presence of …… in the seed is linked with dormancy.

A. Starch
B. Abscisic acid
C. Ethene
D. Gibberellins
Ans. B

8. What is the chemical nature of auxins?

A. Acetic acid
B. Indole acetic acid
C. Naphthalene acetic acid
D. None of the above
Ans. B

9. Which is fruit ripening hormone?

A. Ethylene
B. Auxin
C. Traumatic
D. Cytokinins
Ans. A

10. ……… breaks seed and bud dormancy in the plant?

A. Auxin
B. Gibberellin
C. Cytokinin
D. Ethylene
Ans. B

11. Which hormone aids in the cell division in the presence of auxins?

A. Ethylene
B. Cytokinins
C. Florigens
D. Auxins
Ans. B

12. State the name of plant hormone which enhances cambium activity in the wooden plants?

A. Gibberellins
B. Auxins
C. Cytokinins
D. Ethylene
Ans. A

13. Seed germination is controlled by ………. plant hormone.

A. Gibberellins
B. Auxins
C. Cytokinins
D. Ethylene
Ans. A

14. ……… is the stress hormone of plants.

A. Abscisic acid
B. Auxins
C. Cytokinins
D. Ethylene
Ans. A

15. Which plant hormone is used in the whisky industry?

A. IAA
B. NAA
C. ABA
D. GA3
Ans. D

B. Answer the questions below.

1. Name any four plant hormones.
A. Auxins, Gibberellins, Cytokinins, and Abscisic acid are the four main plant hormones.

2. Which plant hormone is used to treat dwarfism in plants?
A. Gibberellins are the plant hormones that can be used to overcome and treat dwarfism in plants.

3. State two commercial applications of auxins.
A. Synthetic auxins including Naphthalene acetic acid and Indole propionic acid are used to promote parthenocarpy and fruiting in plants. The 2,4 dichloro phenoxy acetic acid is used as a selective weed killer to eradicate broad-leaved species.

4. Define parthenocarpy and which plant induces it.
A. The process of development of fruit without fusion of male and female gametes (fertilization) is known as parthenocarpy. Two plant hormones i.e., auxins, and gibberellins are well known to induce parthenocarpy, while cytokinins seldom induce parthenocarpy.

5. Which hormones delay and enhance the ripening process in fruits?
A. Plant hormone gibberellins are known to delay the fruit ripening process, while ethylene plant hormone enhances the fruit ripening process.

C. Match the description to appropriate plant hormone.

1	Gaseous hormone induces fruit ripening	Gibberellins
2	Activate amylase enzyme during seed germination	Auxins
3	Synthesized at the tip of the plant and moves down to show its effect	Ethylene
4	Promote lateral root growth and development	Abscisic Acid
5	Helps plant to cope with physiological stress	Cytokinin
Ans. 1, Ethylene; 2, Gibberellins; 3, Auxins; 4, Cytokinin; 5, Abscisic Acid

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