Class 10th Science Chapter 6 – Control and Coordination | Plant Hormones and Plant Movements

🌱 Control and Coordination

Plant Hormones and Plant Movements | पादप हार्मोन एवं पादप गतियाँ | Class 10 Science | CBSE + Foundation + Competitive

🌿 Plant Hormones and Plant Movements

1. Plant Hormones – पादप हार्मोन

Plant hormones are chemical substances produced naturally in plants that control and coordinate various activities such as growth, development, cell division, fruit ripening and responses to environmental stimuli.

पादप हार्मोन वे रासायनिक पदार्थ हैं जो पौधों में प्राकृतिक रूप से बनते हैं और वृद्धि, विकास, कोशिका विभाजन, फल पकने तथा बाहरी उद्दीपनों के प्रति प्रतिक्रियाओं को नियंत्रित एवं समन्वित करते हैं।

Important plant hormones:

Auxin
Cell elongation & phototropism

Gibberellin
Stem growth

Cytokinin
Cell division

Abscisic Acid
Growth inhibition & stress

Ethylene
Fruit ripening

2. Auxin – ऑक्सिन

Auxin is a plant hormone mainly associated with cell elongation and directional growth responses.

Auxin is produced mainly in growing regions such as the shoot tips.

Important functions:

• Promotes cell elongation.
• Helps in shoot growth.
• Plays an important role in phototropism.
• Helps coordinate differential growth in plant organs.

Animated Auxin Redistribution During Phototropism

3. Phototropism – प्रकाशानुवर्तन

The directional growth of a plant part in response to light is called phototropism.

Positive phototropism: Growth towards light.
Example: Shoot grows towards light.

Negative phototropism: Growth away from light.

Light → Auxin redistribution → Unequal growth → Shoot bends towards light

4. Role of Auxin in Phototropism

When light falls on one side of a shoot:

1. Light is detected by the growing shoot.
2. Auxin becomes unevenly distributed.
3. More auxin reaches the shaded side of the shoot.
4. Cells on the shaded side elongate more.
5. This causes unequal growth.
6. The shoot bends towards the light.

5. Gibberellins – जिबरेलिन

Gibberellins are plant hormones that promote growth, particularly stem elongation.

Main functions:

• Promote stem elongation.
• Promote growth of plant parts.
• Participate in seed germination and other developmental processes.

Gibberellin → Stem elongation → Increased plant height

6. Cytokinins – साइटोकाइनिन

Cytokinins are plant hormones that promote cell division.

Important functions:

• Promote cell division.
• Support growth of actively dividing tissues.
• Can delay ageing of some plant tissues.

Cytokinin → Cell Division

7. Abscisic Acid (ABA) – एब्सिसिक अम्ल

Abscisic acid, commonly abbreviated as ABA, generally acts as a growth-inhibiting hormone.

Important functions:

• Inhibits growth in several situations.
• Promotes seed dormancy.
• Helps plants respond to water stress.
• Promotes stomatal closure during water stress.

ABA → Growth inhibition + Dormancy + Stress response

8. Ethylene – एथिलीन

Ethylene is a gaseous plant hormone.

Major functions:

• Promotes fruit ripening.
• Influences ageing of plant tissues.
• Participates in leaf and flower shedding.
• Regulates several developmental responses.

Ethylene → Fruit Ripening

9. Plant Hormones – Comparison Table

Hormone	Main Function	Memory Trick
Auxin	Cell elongation and phototropism	Auxin = Elongation
Gibberellin	Stem elongation	Gibberellin = Height
Cytokinin	Cell division	Cytokinin = Cells divide
ABA	Growth inhibition, dormancy and stress response	ABA = Brake
Ethylene	Fruit ripening	Ethylene = Ripening

10. Plant Movements – पादप गतियाँ

Plants show different movements in response to environmental stimuli.

Plant movements may be:

• Tropic movements – directional responses to stimuli.
• Nastic movements – responses generally independent of the direction of stimulus.

11. Tropic Movements – अनुवर्ती गतियाँ

A tropic movement is a directional growth response of a plant part to an external stimulus.

Major types:

• Phototropism – Light
• Geotropism – Gravity
• Hydrotropism – Water
• Thigmotropism – Touch
• Chemotropism – Chemicals

12. Geotropism / Gravitropism – गुरुत्वानुवर्तन

The directional growth response of a plant to gravity is called geotropism or gravitropism.

Root: Positive geotropism.
Shoot: Negative geotropism.

Root → + Geotropism
Shoot → – Geotropism

13. Hydrotropism – जलानुवर्तन

The directional growth response of a plant part to water or moisture is called hydrotropism.

Roots generally grow towards a region containing more moisture.

Therefore, roots generally show positive hydrotropism.

14. Thigmotropism – स्पर्शानुवर्तन

The directional growth response of a plant part to touch is called thigmotropism.

Example: Tendrils of climbing plants coil around a support after contact with it.

15. Chemotropism – रसायनानुवर्तन

The directional growth response to a chemical stimulus is called chemotropism.

Example: Pollen tube grows towards the ovule under the influence of chemical signals.

16. Types of Plant Movements – Complete Table

Movement	Stimulus	Example
Phototropism	Light	Shoot bends towards light
Geotropism	Gravity	Root grows downward
Hydrotropism	Water	Root grows towards moisture
Thigmotropism	Touch	Tendril coils around support
Chemotropism	Chemical	Pollen tube grows towards ovule

17. Nastic Movement – नैस्टिक गति

Nastic movements are plant movements in which the response generally does not depend on the direction from which the stimulus is applied.

Some nastic movements occur due to changes in turgor pressure rather than growth.

Example: Folding of leaves of Mimosa pudica on touching.

Animated Mimosa pudica – Touch Response

18. Tropic vs Nastic Movement

Tropic Movement	Nastic Movement
Directional response.	Generally non-directional response.
Often associated with growth.	May result from changes in turgor.
Usually relatively slow.	Some responses are rapid.
Example: Phototropism.	Example: Mimosa leaf folding.

19. 30 MCQs – Multiple Choice Questions

Q1. Which plant hormone promotes cell elongation?

A) Auxin

B) ABA

C) Ethylene

D) Cytokinin

Answer: A

Q2. Which hormone mainly promotes cell division?

A) Ethylene

B) Cytokinin

C) ABA

D) Auxin

Answer: B

Q3. Which hormone promotes stem elongation?

A) ABA

B) Ethylene

C) Gibberellin

D) Cytokinin

Answer: C

Q4. Which plant hormone is gaseous?

A) Auxin

B) Cytokinin

C) ABA

D) Ethylene

Answer: D

Q5. Fruit ripening is promoted by:

A) Ethylene

B) Auxin

C) Cytokinin

D) ABA

Answer: A

Q6. Which hormone generally inhibits growth?

A) Gibberellin

B) ABA

C) Auxin

D) Cytokinin

Answer: B

Q7. Growth of shoot towards light is called:

A) Geotropism

B) Hydrotropism

C) Phototropism

D) Chemotropism

Answer: C

Q8. In phototropism, the important growth hormone is:

A) Ethylene

B) ABA

C) Cytokinin

D) Auxin

Answer: D

Q9. Root growing in the direction of gravity shows:

A) Positive geotropism

B) Negative geotropism

C) Negative hydrotropism

D) Positive phototropism

Answer: A

Q10. Root growing towards water shows:

A) Phototropism

B) Positive hydrotropism

C) Negative geotropism

D) Thigmotropism

Answer: B

Q11. Tendrils coiling around a support show:

A) Geotropism

B) Phototropism

C) Thigmotropism

D) Hydrotropism

Answer: C

Q12. Pollen tube growth towards ovule is an example of:

A) Hydrotropism

B) Geotropism

C) Phototropism

D) Chemotropism

Answer: D

Q13. Which hormone promotes seed dormancy?

A) ABA

B) Auxin

C) Cytokinin

D) Ethylene

Answer: A

Q14. Which hormone helps plants respond to water stress?

A) Cytokinin

B) ABA

C) Gibberellin

D) Ethylene

Answer: B

Q15. Which hormone can delay ageing of some plant tissues?

A) ABA

B) Ethylene

C) Cytokinin

D) Gibberellin

Answer: C

Q16. Which movement is caused by gravity?

A) Phototropism

B) Chemotropism

C) Thigmotropism

D) Geotropism

Answer: D

Q17. The stimulus for phototropism is:

A) Light

B) Water

C) Gravity

D) Touch

Answer: A

Q18. The stimulus for hydrotropism is:

A) Gravity

B) Water

C) Light

D) Chemical

Answer: B

Q19. The stimulus for thigmotropism is:

A) Light

B) Gravity

C) Touch

D) Water

Answer: C

Q20. The stimulus for chemotropism is:

A) Water

B) Light

C) Gravity

D) Chemical

Answer: D

Q21. Which is an example of a nastic movement?

A) Mimosa leaf folding

B) Root growing downward

C) Shoot bending towards light

D) Root growing towards water

Answer: A

Q22. Mimosa leaf folding mainly involves:

A) Cell division

B) Changes in turgor

C) Fruit ripening

D) Stem elongation

Answer: B

Q23. Which hormone is commonly called a growth inhibitor?

A) Auxin

B) Gibberellin

C) ABA

D) Cytokinin

Answer: C

Q24. Which hormone is associated with stem height?

A) Ethylene

B) ABA

C) Cytokinin

D) Gibberellin

Answer: D

Q25. Which plant hormone is associated with cell elongation?

A) Auxin

B) ABA

C) Ethylene

D) Cytokinin

Answer: A

Q26. Which pair is correctly matched?

A) ABA – cell division

B) Cytokinin – cell division

C) Ethylene – stem elongation

D) Auxin – fruit ripening

Answer: B

Q27. Shoot generally shows which response to gravity?

A) Positive geotropism

B) Positive hydrotropism

C) Negative geotropism

D) Positive chemotropism

Answer: C

Q28. Which movement is generally associated with differential growth?

A) Mimosa leaf folding

B) Turgor movement

C) Non-directional movement

D) Phototropism

Answer: D

Q29. Which sequence is correct for phototropism?

A) Light → Auxin redistribution → Unequal growth → Bending

B) Water → ABA → Cell division → Bending

C) Gravity → Ethylene → Ripening

D) Touch → Cytokinin → Fruit formation

Answer: A

Q30. Which hormone is most directly associated with fruit ripening?

A) Auxin

B) Ethylene

C) Cytokinin

D) ABA

Answer: B

20. 2 Marks Questions – 2 अंक

2 Marks Q1. What are plant hormones?

Plant hormones are chemical substances produced in plants that regulate growth, development and responses to environmental stimuli.

2 Marks Q2. What is phototropism?

Phototropism is the directional growth of a plant part in response to light.

2 Marks Q3. Name two plant hormones.

Auxin and gibberellin. Other examples are cytokinin, ABA and ethylene.

2 Marks Q4. What is geotropism?

Geotropism is the directional growth response of a plant part to gravity.

2 Marks Q5. What is hydrotropism?

Hydrotropism is the directional growth response of a plant part to water or moisture.

21. 3 Marks Questions – 3 अंक

3 Marks Q6. Write three functions of auxin.

Auxin promotes cell elongation, supports shoot growth and plays an important role in phototropism.

3 Marks Q7. Write the functions of gibberellin, cytokinin and ethylene.

Gibberellin promotes stem elongation, cytokinin promotes cell division and ethylene promotes fruit ripening.

3 Marks Q8. Differentiate positive and negative phototropism.

Positive phototropism is growth towards light, while negative phototropism is growth away from light.

3 Marks Q9. Explain positive and negative geotropism.

Root growth in the direction of gravity is positive geotropism. Shoot growth opposite to gravity is negative geotropism.

3 Marks Q10. What is thigmotropism? Give an example.

Thigmotropism is directional growth in response to touch. Tendrils of climbing plants coiling around a support are an example.

22. 4 Marks Questions – 4 अंक

4 Marks Q11. Explain the role of auxin in phototropism.

When light falls from one side, auxin becomes unevenly distributed in the shoot. More auxin accumulates on the shaded side. Cells there elongate more, causing unequal growth. Consequently, the shoot bends towards the light.

4 Marks Q12. Write four types of tropic movements with their stimuli.

Phototropism – light.
Geotropism – gravity.
Hydrotropism – water.
Thigmotropism – touch.

4 Marks Q13. Explain the functions of four plant hormones.

Auxin promotes cell elongation. Gibberellin promotes stem elongation. Cytokinin promotes cell division. ABA inhibits growth and helps in dormancy and stress response.

4 Marks Q14. Differentiate between tropic and nastic movements.

Tropic movements are directional responses and are often growth-dependent. Nastic movements generally do not depend on stimulus direction and may involve changes in turgor. Phototropism is tropic, whereas Mimosa leaf folding is nastic.

4 Marks Q15. Explain hydrotropism and chemotropism.

Hydrotropism is growth in response to water; roots generally grow towards moisture. Chemotropism is growth in response to chemicals; pollen tube growth towards the ovule is a common example.

23. 5 Marks Questions – 5 अंक

5 Marks Q16. Explain the five major plant hormones and their functions.

Auxin: Cell elongation and phototropism.

Gibberellin: Stem elongation and growth.

Cytokinin: Cell division.

ABA: Growth inhibition, dormancy and stress response.

Ethylene: Fruit ripening and developmental responses.

5 Marks Q17. Explain different types of tropic movements.

Phototropism is response to light. Geotropism is response to gravity. Hydrotropism is response to water. Thigmotropism is response to touch. Chemotropism is response to chemical stimuli.

5 Marks Q18. Explain phototropism in a shoot.

A shoot receiving light from one side shows unequal distribution of auxin. More auxin accumulates on the shaded side. The shaded-side cells elongate more, producing unequal growth. The shoot consequently bends towards the light.

5 Marks Q19. Explain the role of ABA in plants.

ABA is generally a growth-inhibiting hormone. It promotes seed dormancy, helps plants respond to water stress and promotes stomatal closure during water shortage.

5 Marks Q20. Explain the response of Mimosa pudica to touch.

When Mimosa leaves are touched, they fold or droop rapidly. This response is mainly due to changes in water content and turgor pressure in specialised cells rather than growth. It is therefore different from growth-dependent phototropism.

24. 6 Marks Questions – 6 अंक

6 Marks Q21. Explain plant hormones in detail.

Plant hormones are chemical messengers that regulate growth and development.

Auxin: Promotes cell elongation and phototropism.
Gibberellin: Promotes stem elongation.
Cytokinin: Promotes cell division.
ABA: Inhibits growth, promotes dormancy and stress responses.
Ethylene: Promotes fruit ripening and affects several developmental processes.

6 Marks Q22. Describe the mechanism of phototropism.

1. Light falls on one side of the shoot.
2. The plant detects the light stimulus.
3. Auxin becomes unevenly distributed.
4. More auxin accumulates on the shaded side.
5. Cells on the shaded side elongate more.
6. Unequal growth causes the shoot to bend towards the light.

6 Marks Q23. Explain five types of tropic movements with examples.

Phototropism: Response to light; shoot bends towards light.

Geotropism: Response to gravity; roots show positive geotropism.

Hydrotropism: Response to water; roots grow towards moisture.

Thigmotropism: Response to touch; tendrils coil around support.

Chemotropism: Response to chemicals; pollen tube grows towards ovule.

6 Marks Q24. Compare tropic and nastic movements in plants.

Tropic Movement	Nastic Movement
Directional response.	Generally independent of direction.
Often caused by differential growth.	May occur because of turgor changes.
Usually slower.	Some are rapid.
Example: Phototropism.	Example: Mimosa leaf folding.

6 Marks Q25. Explain how roots and shoots respond to different stimuli.

Roots generally show positive geotropism because they grow in the direction of gravity. They also generally show positive hydrotropism because they grow towards moisture. Shoots generally show positive phototropism by growing towards light and negative geotropism by growing opposite to gravity.

6 Marks Q26. Explain the importance of plant movements.

Plant movements help plants respond to environmental conditions. Phototropism helps shoots obtain light. Hydrotropism helps roots reach water. Geotropism helps establish proper root and shoot orientation. Thigmotropism helps climbing plants obtain support. These responses improve survival and growth.

6 Marks Q27. Explain the difference between growth movement and turgor movement.

Growth movements occur because different regions of a plant grow at different rates and are usually slow and irreversible. Phototropism is an example. Turgor movements occur because of changes in water content and turgor pressure in cells and can be rapid. Mimosa leaf folding is an example.

6 Marks Q28. Explain the functions of auxin, gibberellin, cytokinin, ABA and ethylene.

Auxin promotes cell elongation and phototropism. Gibberellin promotes stem elongation. Cytokinin promotes cell division. ABA inhibits growth, promotes dormancy and helps during water stress. Ethylene promotes fruit ripening and influences several developmental processes.

6 Marks Q29. Draw and explain phototropism in a plant shoot.

The diagram should show:

1. Light source on one side.
2. Shoot tip.
3. Unequal auxin distribution.
4. Greater elongation on shaded side.
5. Curvature towards the light.

Sequence:
Light → Auxin redistribution → Unequal elongation → Shoot bends towards light.

6 Marks Q30. Explain how plant hormones and plant movements help in coordination.

Plant hormones coordinate growth, development and responses. Auxin regulates elongation and phototropism; gibberellin promotes stem growth; cytokinin promotes cell division; ABA regulates growth inhibition, dormancy and stress response; ethylene promotes fruit ripening. Plant movements such as phototropism, geotropism, hydrotropism and thigmotropism allow plants to respond appropriately to their surroundings.

25. HOTS / Competency Based Questions

HOTS 1: A plant kept near a window bends towards the window. Why?

The shoot receives light from one direction. Auxin redistribution causes greater elongation on the shaded side, so the shoot bends towards the light.

HOTS 2: A root grows towards a moist area. Identify the movement.

Positive hydrotropism.

HOTS 3: Why is Mimosa movement not considered ordinary growth?

Because the rapid leaf folding mainly results from changes in water content and turgor pressure rather than growth.

HOTS 4: A farmer wants to understand why some fruits ripen faster. Which plant hormone is important?

Ethylene.

26. CBSE Golden Points – परीक्षा के लिए महत्वपूर्ण

⭐ Auxin → Cell elongation + Phototropism

⭐ Gibberellin → Stem elongation

⭐ Cytokinin → Cell division

⭐ ABA → Growth inhibition + Dormancy + Stress response

⭐ Ethylene → Fruit ripening

⭐ Phototropism → Light

⭐ Geotropism → Gravity

⭐ Hydrotropism → Water

⭐ Thigmotropism → Touch

⭐ Chemotropism → Chemical stimulus

⭐ Root → Positive Geotropism

⭐ Shoot → Positive Phototropism

⭐ Mimosa → Turgor-based movement

27. One-Line Revision

Question Cue	Answer
Cell elongation?	Auxin
Stem elongation?	Gibberellin
Cell division?	Cytokinin
Growth inhibition?	ABA
Fruit ripening?	Ethylene
Light?	Phototropism
Gravity?	Geotropism
Water?	Hydrotropism
Touch?	Thigmotropism
Chemical?	Chemotropism
Mimosa leaf folding?	Turgor / Nastic movement

28. Diagram Labelling Practice

CBSE परीक्षा के लिए इन diagrams की practice करें:

• Phototropism in shoot
• Geotropism in root and shoot
• Hydrotropism in roots
• Tendril showing thigmotropism
• Mimosa pudica touch response
• Plant hormones and their functions

29. Super Memory Trick

AUXIN = ELONGATION

GIBBERELLIN = HEIGHT

CYTOKININ = CELL DIVISION

ABA = BRAKE

ETHYLENE = RIPENING

PHOTO = LIGHT | GEO = GRAVITY | HYDRO = WATER | THIGMO = TOUCH | CHEMO = CHEMICAL

30. Final Exam Revision

Most Important CBSE Questions:

1. Explain the role of auxin in phototropism.
2. What are plant hormones?
3. Explain the functions of auxin, gibberellin, cytokinin, ABA and ethylene.
4. Explain different types of tropic movements.
5. Differentiate between tropic and nastic movements.
6. Explain the response of Mimosa pudica to touch.
7. Define phototropism, geotropism, hydrotropism and thigmotropism.
8. Why does a shoot bend towards light?
9. Why do roots grow towards water?
10. Explain how plants coordinate without a nervous system.