Chapter 2 – Response and Chemical Co-ordination in Plants Hormones Q&A

Need a quick revision before your exam starts? The topic Response and Chemical Co-ordination in Plants (Hormones) is an important part of your WBBSE Class 10 exam. Here, you will get important questions and answers in very simple English. These questions are based on important topics and common exam patterns. This will help you revise easily, understand clearly, and score better marks in your exam.

Content Structure

1. Multiple choice questions and answers (MCQs)
2. Very short-type questions and answers
- 2A. Fill in the blanks
- 2B. True or false
- 2C. Match the column
- 2D. Single word questions and answers
3. Short-type questions and answers
4. Long-type questions and answers

1. Multiple choice type questions and answers (MCQ):

1. Which hormone mainly helps stem growth?
(a) Gibberellin
(b) Auxin
(c) ABA
(d) Cytokinin

Ans: (a) Gibberellin

2. Which hormone increases seed germination?
(a) Auxin
(b) Gibberellin
(c) ABA
(d) Ethylene

Ans: (b) Gibberellin

3. Which ion is controlled by Gibberellin?
(a) H⁺
(b) Ca²⁺
(c) Na⁺
(d) Mg²⁺

Ans: (b) Ca²⁺

4. Growth of a plant toward light is called:
(a) Negative gravitropism
(b) Positive gravitropism
(c) Negative phototropism
(d) Positive phototropism

Ans: (d) Positive phototropism

5. “Circadian” means:
(a) Auxin
(b) Tropism
(c) Nastic
(d) Day–night cycle

Ans: (d) Day–night cycle

6. Which hormone slows plant growth?
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Gibberellin

Ans: (a) Abscisic acid

7. Darwin studied which hormone in phototropism?
(a) ABA
(b) Auxin
(c) Cytokinin
(d) Ethylene

Ans: (b) Auxin

8. IAA is a natural form of which hormone?
(a) ABA
(b) Auxin
(c) Cytokinin
(d) Ethylene

Ans: (b) Auxin

9. Which is an effect of auxin?
(a) Helps cuttings make roots
(b) Helps fruits grow
(c) Stops fruits from falling early
(d) All of these

Ans: (d) All of these

10. Which plant hormone is a gas?
(a) ABA
(b) Auxin
(c) Cytokinin
(d) Ethylene

Ans: (d) Ethylene

11. Which hormone causes seed and bud dormancy?
(a) ABA
(b) Auxin
(c) Cytokinin
(d) Ethylene

Ans: (a) ABA

12. The term “phytochrome” means:
(a) Auxin
(b) Tropism
(c) Nastic
(d) Plant + colour

Ans: (d) Plant + colour

13. Gravitropism in roots is:
(a) Roots growing downward
(b) Caused by statoliths
(c) Controlled by auxins
(d) All of these

Ans: (d) All of these

14. Cytokinins:
(a) Promote cell division
(b) Work with auxin in tissue culture
(c) Help in tissue development
(d) All are true

Ans: (d) All are true

15. Gibberellin promotes:
(a) Seed germination
(b) Dormancy
(c) Leaf fall
(d) Root elongation

Ans: (a) Seed germination

16. Hormone for cell division is:
(a) IAA
(b) NAA
(c) Cytokinin
(d) Gibberellic acid

Ans: (c) Cytokinin

17. Leaf fall can be prevented by:
(a) ABA
(b) Auxin
(c) Florigen
(d) Cytokinin

Ans: (d) Cytokinin

18. ABA controls:
(a) Cell division
(b) Leaf fall and dormancy
(c) Shoot growth
(d) Cell wall formation

Ans: (b) Leaf fall and dormancy

19. Chemical that causes flowering is:
(a) Gibberellin
(b) Kinetin
(c) Florigen
(d) IBA

Ans: (c) Florigen

20. Apical dominance hormone is:
(a) IAA
(b) GA
(c) ABA
(d) Florigen

Ans: (a) IAA

21. ABA causes:
(a) Stomatal closure
(b) Leaf expansion
(c) Stem elongation
(d) Root elongation

Ans: (a) Stomatal closure

22. Bananas can be kept fresh by using:
(a) Room temperature
(b) Fridge
(c) Ascorbic acid solution
(d) Freezing

Ans: (c) Ascorbic acid solution

23. Which hormone delays ageing?
(a) Cytokinin
(b) Auxin
(c) Gibberellin
(d) Abscisic acid

Ans: (a) Cytokinin

24. Which breaks potato tuber dormancy?
(a) Gibberellin
(b) IAA
(c) ABA
(d) Zeatin

Ans: (a) Gibberellin

25. Coconut milk factor is:
(a) Auxin
(b) Gibberellin
(c) ABA
(d) Cytokinin

Ans: (d) Cytokinin

26. Florigen is a type of:
(a) Plant hormone
(b) Animal hormone
(c) Enzyme
(d) Vitamin

Ans: (a) Plant hormone

27. A hormone is a:
(a) Enzyme
(b) Physical co-ordinator
(c) Receptor
(d) Chemical co-ordinator

Ans: (d) Chemical co-ordinator

28. An example of a natural hormone is:
(a) IPA
(b) IBA
(c) NAA
(d) Auxin

Ans: (d) Auxin

29. A non-nitrogenous plant hormone is:
(a) Cytokinin
(b) Auxin
(c) Gibberellin
(d) All of these

Ans: (c) Gibberellin

30. A synthetic hormone is:
(a) NAA
(b) IAA
(c) GA
(d) Cytokinin

Ans: (a) NAA

31. A gaseous hormone is:
(a) Auxin
(b) Ethylene
(c) IPA
(d) Dormin

Ans: (b) Ethylene

32. Experiment with auxin was first done on:
(a) Wheat plant
(b) Pea plant
(c) Paddy plant
(d) Oat plant

Ans: (d) Oat plant

33. Flow of auxin in a plant is mostly:
(a) Downward
(b) Lateral
(c) Upward
(d) In all directions

Ans: (a) Downward

34. Flow of gibberellins in plants is:
(a) Upward
(b) Downward
(c) Lateral
(d) Both A & B

Ans: (d) Both A & B

35.. Which hormone increases cell size?
(a) Auxin
(b) Ethylene
(c) Gibberellin
(d) Cytokinin

Ans: (c) Gibberellin

36. Gibberella fujikuroi is a:
(a) Alga
(b) Moss
(c) Bacterium
(d) Fungus

Ans: (d) Fungus

37. Main cytokinins are:
(a) 2,4-D
(b) Zeatin and Kinetin
(c) 2,4,5-T
(d) GA₃ and GA₂

Ans: (b) Zeatin and Kinetin

38. Chemical composition of gibberellin is:
(a) C, H, O and N
(b) C, H and O
(c) C, H, N and S
(d) C, S and P

Ans: (b) C, H and O

39. Which is a nitrogenous acidic plant hormone?
(a) Auxin
(b) Aldosterone
(c) Ethylene
(d) Oxytocin

Ans: (a) Auxin

40. Auxin is made from which amino acid?
(a) Tyrosine
(b) Lysine
(c) Tryptophan
(d) Valine

Ans: (c) Tryptophan

41. Which hormone helps in cell division?
(a) Florigen
(b) Oxytocin
(c) Cytokinin
(d) Ethylene

Ans: (c) Cytokinin

42. Gibberellin was discovered by:
(a) Ronald Ross
(b) Teijiro Yabuta
(c) Fredrick Sanger
(d) Elichi Kurosawa

Ans: (d) Elichi Kurosawa

43. Which group of hormones is called phytohormones?
(a) Plant hormones
(b) Animal hormones
(c) None of these
(d) Both

Ans: (a) Plant hormones

44. Gibberellin was discovered from which organism?
(a) Rice plant
(b) Wheat plant
(c) Fungus
(d) Algae

Ans: (c) Fungus

2. Very short-type questions and answers

2A. Fill in the blanks

1. ___________ hormones are called “growth regulators”. (plant)
2. Growth, seed germination and stopping early leaf fall are done by ___________. (auxin)
3. ___________ are found naturally in seeds and young seedlings. (Gibberellins)
4. Gibberellins are ___________ plant hormones. (terpenoid)
5. Auxin promotes ___________ dominance. (apical)
6. Tropic movements are controlled by ___________. (auxin)
7. The hormone used for killing weeds is ___________. (2,4-D)
8. Indole Acetic Acid is the chemical name of ___________. (auxin)
9. ___________ slows ageing in plants. (Cytokinin)
10. The word hormone comes from ___________ language. (Greek)
11. The first discovered hormone was ___________. (secretin)
12. Root growth is helped by ___________. (auxin)
13. The main coordinating substance in plants is ___________. (hormone)
14. ___________ increases in the ovary after fertilisation. (auxin)
15. ___________ is an artificial weed-killing hormone. (2,4-D)
16. Cytokinin has an ___________ type nitrogen base. (adenine)
17. The first plant hormone discovered was ___________. (auxin)
18. The first discovered plant hormone is ___________. (auxin)
19. The gas that ripens fruits is ___________. (ethylene)
20. The main growth regulator of plants is ___________. (auxin)
21. ___________ helps in blooming of flowers. (Gibberellin)
22. A small amount of auxin helps ___________ grow. (roots)

2B. True or false

1. Florigen makes fruits grow. (False)
2. Cytokinin stops young leaves from falling early. (True)
3. Cytokinin helps the stem become longer. (False)
4. Gibberellin makes plants taller by stretching the stem. (True)
5. Gibberellin controls bending of plants. (False)
6. Cytokinin is also called Kinin. (True)
7. Hormones stop working after they finish their job. (True)
8. Artificial hormones are also called plant growth regulators. (True)
9. Phototropism means movement toward gravity. (False)
10. Cytokinin helps cells divide. (True)
11. Touch-me-not plant closes its leaves because of auxin. (False)

2C. Match the column

1. Match the following items in List I with correct items in List II.

A	B
1. Growing organs of plant	A. Ethylene
2. Endosperm of seed	B. Florigen
3. Matured cotyledon	C. Auxin
4. Blooming of flower	D. Gibberellin
5. Fruit ripening	E. Cytokinin
6. Weedicide	F. ABA
	G. 2, 4-D

Ans:

1. Growing organs of plant	C. Auxin
2. Endosperm of seed	E. Cytokinin
3. Matured cotyledon	D. Gibberellin
4. Blooming of flower	B. Florigen
5. Fruit ripening	A. Ethylene
6. Weedicide	G. 2,4-D

2. Match the following items in List I with correct items in List II.

A	B
1. Helps in growth of plant	A. Cytokinin
2. Breaks dormancy of seeds and buds	B. Auxin
3. Helps in cell division and delays senescence in plant	C. Abscisic acid
4. Helps in ripening of seeds	D. Gibberellin
5. Reduces rate of transpiration in plants	E. Florigen
6. Hinders plant growth	F. Abscisic acid
	G. Ethylene

Ans:

A	B
1. Helps in growth of plant	B. Auxin
2. Breaks dormancy of seeds and buds	D. Gibberellin
3. Helps in cell division and delays ageing	A. Cytokinin
4. Helps in ripening of seeds	G. Ethylene
5. Reduces rate of transpiration	F. Abscisic acid
6. Hinders plant growth	C. Abscisic acid

2D. Single word or single sentence questions and answers

1. Which hormones are called growth regulators?
Ans: Plant hormones / Phytohormones

2. Mention the source of Auxin.
Ans: Apical meristem

3. What is the chemical name of Auxin?
Ans: Indole Acetic Acid

4. What is the full name of IAA?
Ans: Indole-3-Acetic Acid

5. Which hormone checks early fall of leaves and fruits?
Ans: Auxin

6. Mention the source of gibberellins.
Ans: Fungus Gibberella fujikuroi

7. Name two main functions of Gibberellin.
Ans: Stem elongation and breaking seed dormancy

8. Which hormone is found in green coconut water?
Ans: Cytokinin

9. Name one function of cytokinin.
Ans: Promotes cell division

10. Which hormone retards ageing (senescence) in plants?
Ans: Cytokinin

11. What is a phytohormone?
Ans: A hormone produced by plants

12. Mention the place of action of auxins.
Ans: Shoot tip and root tip

13. Is there any ductless gland present in plant?
Ans: No

14. Name one hormone which is gaseous in nature.
Ans: Ethylene

15. What is the meaning of the term ‘hormone’?
Ans: The term ‘hormone’ means ‘to stimulate’ or ‘to set in motion’.

16. Name a plant hormone that hinders plant growth.
Ans: Abscisic acid (ABA)

17. Mention the empirical formula of auxin.
Ans: C10H9O2N

18. Name two growth regulators of plants.
Ans: Auxin and gibberellin

19. What is the chemical name of gibberellin?
Ans: Gibberellic acid.

20. Write down the empirical formula of cytokinin.
Ans: C10H9N5O

21. Which phytohormone helps in apical and lateral growth of a plant?
Ans: Auxin

22. What is the full form of IAA?
Ans: Indole Acetic Acid

23. Which phytohormone holds up senescence plants?
Ans: Cytokinin

24. What is the full form of NAA?
Ans: Naphthalene Acetic Acid

25. Write the full form of 2, 4-D.
Ans: 2, 4-Dichlorophenoxy acetic acid

26. What is the full form of IPA?
Ans: Indole Propionic Acid

27. Write the full form of 2,4,5-T.
Ans: 2,4,5-Trichlorophenoxy acetic acid.

28. Give one example of synthetic cytokinin.
Ans: Benzyl Amino Purine (BAP)

29. Which phytohormone instigates the growth of internodes?
Ans: Gibberellin

30. Name one synthetic Auxin used to make seedless fruits.
Ans: NAA.

31. Name one Auxin that can form roots in plant tissue culture.
Ans: IAA.

32. Name a synthetic Auxin used as a weed killer.
Ans: 2,4-D.

33. Name the hormone that causes bolting in plants.
Ans: Gibberellin.

34. Name the meristems responsible for primary growth.
Ans: Root tip and shoot tip.

35. Full form of IAA?
Ans: Indole Acetic Acid.

36. What is a synthetic hormone?
Ans: A hormone made in factories, not in plants.

37. Which hormone helps in optical dormancy?
Ans: Auxin.

38. What is Cytokinin?
Ans: A plant hormone that helps cells divide.

39. Name a natural Auxin.
Ans: IAA.

40. Which hormone is antiauxin?
Ans: Cytokinin.

41. Which hormone removes dwarfness in plants?
Ans: Gibberellin.

42. What are growth inhibitors?
Ans: Hormones that slow down or stop plant growth.

43. Which phytohormone reduces transpiration?
Ans: ABA.

44. Name the gaseous plant hormone.
Ans: Ethylene.

45. Name the hormone that breaks seed dormancy.
Ans: Gibberellin.

3. Short-type questions and answers

[Each questions carries 2 marks]

1. What is hormone?
Ans: A hormone is a chemical messenger that controls different activities of living organisms.

2. What do you mean by ‘growth regulators’?
Ans: Growth regulators are plant hormones that control growth, development, and movements in plants.

3. What is phytohormone?
Ans: A phytohormone is a hormone made by plants to control their growth and development.

4. Name one natural and one artificial plant hormone.
Ans: Natural: Auxin (IAA)
Artificial: NAA

5. What are the chemical name and chemical constituents of Auxin?
Ans: Chemical name: Indole-3-Acetic Acid (IAA)
Constituents: Carbon, Hydrogen, Nitrogen, Oxygen

6. What is the chemical name and chemical constituents of Gibberellins?
Ans:
Chemical name: Gibberellic Acid (GA₃)
Constituents: Carbon, Hydrogen, Oxygen

7. Write short notes on Indole Acetic Acid.
Ans: Indole Acetic Acid (IAA) is the main natural auxin in plants. It helps in cell elongation, root formation, apical dominance, and prevents early leaf fall.

8. What is parthenocarpic fruit? How is it formed?
Ans: A parthenocarpic fruit is a seedless fruit formed without fertilisation by applying auxin or gibberellin.

9. How plant hormone controls weed?
Ans: Synthetic auxins like 2,4-D kill broad-leaved weeds without harming crops.

10. Write short note on Auxin.
Ans: Auxin is a major plant hormone that controls cell elongation, root formation, apical dominance, and prevents early leaf and fruit fall.

11. Write short notes on Gibberellins.
Ans: Gibberellins are plant hormones that help in stem elongation, seed germination, breaking dormancy, and producing larger fruits.

12. Write short notes on Cytokinins.
Ans: Cytokinins promote cell division, delay ageing, help in tissue culture, and work with auxin for plant growth.

13. Mention the role of Auxin in rooting and cutting in plant body.
Ans: Auxin helps new roots grow from plant cuttings, making vegetative propagation easier.

4. Long-type questions and answers

[Each question carries 5 marks]

1. Give one animal and one plant hormone with their site of secretion and functions.
Ans: Hormones are chemical substances that help organisms control and coordinate body functions.

Animal hormone – Insulin:
- Site of secretion: Pancreas (specifically the Islets of Langerhans).
- Functions: Insulin controls blood sugar level by helping cells take in glucose. It prevents high blood sugar and maintains energy balance.
Plant hormone – Auxin:
- Site of secretion: Shoot tip and root tip (apical meristem).
- Functions: Auxin helps in cell elongation, bending towards light, root formation, and prevents early leaf and fruit fall.
  Thus, both hormones help organisms grow, develop, and respond to their environment.

2. Why are hormones called chemical messengers?
Ans: Hormones are called chemical messengers because:

They carry messages from one part of the body to another.
They tell organs when to start or stop working.
They regulate activities like growth, digestion, and reproduction.
They travel through blood or plant sap to reach their target.
They help maintain harmony between different organs.
Since they pass information chemically, they are known as chemical messengers.

3. Write the differences between hormones and enzymes.
Ans:

Hormones	Enzymes
Act as chemical messengers	Work as biological catalysts
Act slowly	Act very fast
Needed in very small amounts	Needed in comparatively larger amounts
Produced in one organ and act on another	Usually work where they are produced
Control long-term processes like growth	Help in chemical reactions like digestion

4. Name any three plant hormones and mention where they are produced.
Ans:

Auxin: Produced in shoot tips and young leaves.
Gibberellin: Produced in young leaves, seeds, and some fungi.
Cytokinin: Produced in root tips, young fruits, and found in coconut water.

5. What is auxin? Where is it made? How does it work?
Ans: Auxin is a major plant growth hormone.

Produced in: Shoot tip, root tip, developing seeds.
How it works:
1. Helps cells grow longer.
2. Helps plants bend towards light.
3. Promotes root formation in cuttings.
4. Prevents early leaf and fruit fall.
5. Maintains apical dominance by suppressing side buds.
  Auxin controls most growth activities in plants.

6. Write the differences between Auxin and Gibberellin.
Ans:

Auxin	Gibberellin
Helps in cell elongation	Helps in stem elongation
Controls bending movements	Breaks seed dormancy
Produced in shoot tips	Produced in young leaves and seeds
Prevents leaf/fruit fall	Helps fruits grow bigger
Maintains apical dominance	Promotes flowering

7. What is cytokinin? Mention its source and functions.
Ans: Cytokinin is a plant hormone that promotes cell division.

Source: Root tips, young fruits, corn seeds, coconut water.
Functions:
1. Helps new cells form.
2. Delays ageing in leaves.
3. Promotes side-bud growth.
4. Used in tissue culture for plantlets.
  Cytokinin keeps plants healthy and fresh.

8. Write any three practical uses of plant hormones in agriculture.
Ans:

Auxins: Used for root formation in cuttings and preventing early fruit drop.
Gibberellins: Used to increase fruit size, promote early seed germination, and produce tall plants.
Cytokinin: Keeps vegetables fresh and helps in tissue culture.
Ethylene: Helps ripen fruits like bananas and tomatoes.
2,4-D: Used as a weed killer in crop fields.
These hormones help farmers increase yield and improve crop quality.

9. Name three plant hormones and state their usefulness in agriculture.
Ans:

Auxin: Rooting in cuttings, prevents fruit drop.
Gibberellin: Larger fruits, faster seed germination.
Cytokinin: Keeps leaves fresh, used in tissue culture.
These hormones improve plant growth, fruit size and productivity.

10. How do auxins help a tendril coil around a support?
Ans:

When a tendril touches a support, auxin moves to the side away from the touch.
The untouched side grows faster because it has more auxin.
The touched side grows slower.
This uneven growth causes the tendril to bend.
As growth continues, the tendril coils around the support for climbing.

11. What are the sources of auxin? Mention two functions.
Ans:

Sources: Shoot tips, root tips, young leaves, developing seeds.
Functions:
1. Helps in formation of seedless fruits.
2. Promotes root formation in cuttings.
3. Prevents early leaf and fruit fall.

12. What is the full form of IBA? What is apical dominance?
Ans:

Full form of IBA: Indole Butyric Acid.
Apical dominance:
The apical (top) bud prevents the growth of the side buds because auxin from the top bud suppresses the lower buds. This keeps the plant growing upward.

13. Name five plant hormones and write one function of each.
Ans:

Auxin: Helps in bending towards light.
Gibberellin: Increases stem length.
Cytokinin: Helps in cell division.
Ethylene: Ripens fruits.
Abscisic acid: Causes seed dormancy and closes stomata.