Multiple Choice Questions on Plant Hormones for NEET and Board Exams
Plant hormones are also known as phytohormones. Plant hormones can be described as chemical substances produced in plants that may be transmitted from one region to another and regulate one or more physiological reactions while present in low concentrations. Some of the important plant hormones are – Auxin, Gibberellin, Ethylene, Abscisic acid, and Cytokinin. These hormones are involved in growth and development responses such as cell division, seed formation, flowering, seed formation and abscission.
MCQs on Plant Hormones
Let us learn some information about the planet hormones in the form of multiple choice questions here.
1. Indole-3-acetic acid is the most known and naturally occurring plant hormone of _______ class.
(a) Gibberellin
(b) Auxin
(c) Ethylene
(d) Cytokinin
Ans: Auxin
2. Which of the following hormones is not a growth inhibitor?
(a) Dormin
(b) Abscisic acid
(c) Ethylene
(d) IAA
Ans: IAA
3. ___________ is a gaseous plant hormone.
(a) IBA
(b) Ethylene
(c) Abscisic acid
(d) NAA
Ans: Ethylene
4. A widely used rooting hormone is
(a) 2,4, -D
(b) NAA
(c) 2,4,5 – T
(d) Cytokinin
Ans: NAA
5. The leaf defoliator utilized as “Agent Orange” was
(a) 2,4, -D and 2,4,5 – T
(b) Ethylene
(c) 2,4, -D and NAA
(d) 2,4,5 – T, ethylene and NAA
Ans: 2,4, -D and 2,4,5 – T
6. Transport of auxin is
(a) non-polar
(b) symplast
(c) apoplast
(d) solar
Ans: polar
7. Formation of the nodule is induced by
(a) IAA
(b) NAA
(c) IBA
(d) Both (a) and (c)
Ans: IAA
8. __________is the precursor of Indole-3-acetic acid.
(a) Methionine
(b) Tryptophan
(c) Glycine
(d) Isopentenyl pyrophosphate
Ans: Tryptophan
9. This bioassay that is used to detect the presence of auxin is/are
(a) Only tobacco pith culture
(b) Tobacco pith culture and Avena curvature test
(c) A curvature test related to Tobacco pith culture and Split pea stem
(d) Tests related to Split pea stem curvature and Avena curvature
Ans: Split pea stem curvature test and Avena curvature test
10. Which of these is not a function of auxin?
(a) Inducing callus formation
(b) Inducing dormancy
(c) Enhancing cell division
(d) Maintaining apical dominant
Ans: Inducing dormancy.
FAQs on Plant Hormones MCQs with Answers and Explanations
1. What are plant hormones?
Plant hormones are chemical messengers produced in small amounts that regulate growth, development, and responses in plants. They are also called phytohormones and control processes such as cell division, elongation, flowering, fruit ripening, and stress responses. Unlike animal hormones, plant hormones are not produced by specialized glands and can act locally or be transported to other parts of the plant.
2. What are the five major plant hormones?
The five major plant hormones are Auxins, Gibberellins, Cytokinins, Ethylene, and Abscisic acid (ABA).
- Auxins – Promote cell elongation and apical dominance.
- Gibberellins – Stimulate stem elongation and seed germination.
- Cytokinins – Promote cell division.
- Ethylene – Controls fruit ripening.
- Abscisic acid – Induces dormancy and stress responses.
3. What is the function of auxin in plants?
The main function of auxin is to promote cell elongation in shoots. It is primarily produced in the apical meristem and young leaves.
- Causes stem bending toward light (phototropism).
- Maintains apical dominance by inhibiting lateral buds.
- Promotes root initiation in cuttings.
4. How does gibberellin affect plant growth?
Gibberellins stimulate stem elongation, seed germination, and flowering in some plants. They break seed dormancy by activating enzymes like amylase that convert starch into sugars during germination.
- Increase internode length.
- Promote bolting in rosette plants.
- Enhance fruit size in some crops.
5. What is the role of cytokinins in plants?
Cytokinins primarily promote cell division (cytokinesis) in plant tissues. They are synthesized mainly in roots and transported to shoots.
- Stimulate growth of lateral buds.
- Delay leaf senescence (aging).
- Work antagonistically with auxins to regulate organ formation.
6. Why is ethylene called a stress hormone in plants?
Ethylene is called a stress hormone because it is produced in response to mechanical stress, injury, or infection. It is a gaseous plant hormone that regulates:
- Fruit ripening in climacteric fruits like banana and tomato.
- Leaf and fruit abscission.
- Response to flooding and pathogen attack.
7. What is the function of abscisic acid (ABA)?
Abscisic acid (ABA) mainly induces seed dormancy and helps plants respond to stress conditions. It is known as a growth-inhibiting hormone.
- Closes stomata during water stress.
- Promotes seed dormancy.
- Inhibits growth under unfavorable conditions.
8. What is the difference between auxin and cytokinin?
The main difference between auxin and cytokinin is that auxin promotes cell elongation while cytokinin promotes cell division.
- Auxin: Maintains apical dominance and stimulates root formation.
- Cytokinin: Stimulates lateral bud growth and delays leaf aging.
9. How do plant hormones control seed germination?
Plant hormones control seed germination mainly through the balance between gibberellins and abscisic acid.
- Gibberellins break dormancy and activate enzymes for food mobilization.
- Abscisic acid maintains dormancy and prevents premature germination.
10. Which plant hormone is responsible for fruit ripening?
The plant hormone responsible for fruit ripening is ethylene. It accelerates biochemical changes such as:
- Conversion of starch into sugars.
- Softening of the fruit due to cell wall breakdown.
- Development of color and aroma.
