Class 10th Science Chapter 6 – Control and Coordination | Coordination in Plants

🌱 Control and Coordination

Coordination in Plants | पौधों में समन्वय | Class 10 Science | CBSE + Foundation + Competitive

🌱 Coordination in Plants – पौधों में समन्वय

1. Coordination in Plants – पौधों में समन्वय

Plants do not have a nervous system like animals. They coordinate their activities mainly through plant hormones, growth responses and changes in cells/tissues.

पौधों में जन्तुओं की तरह तंत्रिका तंत्र नहीं होता। पौधे मुख्य रूप से पादप हार्मोन, वृद्धि तथा कोशिकाओं/ऊतकों में होने वाले परिवर्तनों के द्वारा विभिन्न क्रियाओं का समन्वय करते हैं।

Plants respond to external stimuli such as:

• Light – प्रकाश
• Gravity – गुरुत्वाकर्षण
• Water – जल
• Touch – स्पर्श
• Chemicals – रसायन
• Temperature – तापमान

2. How Do Plants Respond to Stimuli?

Plants respond to stimuli through changes in the growth or movement of their parts.

For example, the shoot bends towards light. This is called phototropism.

Roots generally grow towards gravity and water.

Some plant movements occur due to growth, while others occur due to changes in water content or turgor pressure of cells.

Animated Plant Coordination – Stimulus → Response

3. Plant Hormones – पादप हार्मोन

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

Important plant hormones at Class 10 level:

Auxin
Growth & phototropism

Gibberellin
Stem growth

Cytokinin
Cell division

Abscisic Acid (ABA)
Growth inhibition

Ethylene
Fruit ripening

4. Auxin – ऑक्सिन

Auxin is a plant hormone that promotes cell growth, especially in shoots, and plays an important role in phototropism.

Auxin is produced mainly in the shoot tips.

When light falls from one side:

• Auxin redistributes towards the shaded side of the shoot.
• Cells on the shaded side elongate more.
• This unequal growth causes the shoot to bend towards light.

Unequal auxin distribution → Unequal cell elongation → Bending of shoot

5. Phototropism – प्रकाशानुवर्तन

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

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

Negative phototropism: Growth away from light.
Roots generally show negative phototropism.

Shoot → Positive Phototropism → Towards Light

6. Geotropism / Gravitropism – गुरुत्वानुवर्तन

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

Roots: Positive geotropism – grow in the direction of gravity.

Shoots: Negative geotropism – grow opposite to gravity.

Root → + Geotropism
Shoot → – Geotropism

7. Hydrotropism – जलानुवर्तन

The directional growth of roots in response to water or moisture is called hydrotropism.

Roots generally grow towards a region containing more water.

Therefore, roots show positive hydrotropism.

8. Thigmotropism – स्पर्शानुवर्तन

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

Example: Tendrils of pea and other climbing plants coil around a support when they come in contact with it.

9. Chemotropism – रसायनानुवर्तन

The directional growth of a plant part in response to a chemical stimulus is called chemotropism.

Example: Growth of pollen tube towards the ovule is a commonly cited example of positive chemotropism.

10. Types of Tropic Movements

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

11. Gibberellins – जिबरेलिन

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

Important functions:

• Promote stem growth.
• Promote elongation of plant parts.
• Help in seed germination and development in suitable conditions.

12. Cytokinins – साइटोकाइनिन

Cytokinins promote cell division.

They are especially important in actively dividing plant tissues.

They can also delay ageing of some plant tissues.

13. Abscisic Acid (ABA) – एब्सिसिक अम्ल

Abscisic acid is generally considered a growth-inhibiting plant hormone.

Functions include:

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

14. Ethylene – एथिलीन

Ethylene is a gaseous plant hormone.

Important functions:

• Promotes fruit ripening.
• Influences ageing and falling of leaves/flowers.
• Participates in several developmental responses.

15. Plant Hormones – Quick Comparison

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

16. Growth Movement vs Non-Growth Movement

Plant responses can occur through different mechanisms.

Growth-dependent movement:
Occurs because different regions of a plant grow at different rates.
Example: Phototropic bending of shoot.

Movement due to changes in turgor:
Occurs due to changes in water content and pressure in cells.
Example: Folding of leaves of Mimosa pudica when touched.

17. Mimosa pudica – Touch Response

The leaves of Mimosa pudica fold or droop when touched.

This movement is not primarily due to growth. It results from rapid changes in water content/turgor pressure in specialised cells.

Therefore, it is different from slow growth movements such as phototropism.

Animated Touch Response – Mimosa

18. Tropic Movement vs Nastic Movement

Tropic Movement	Nastic Movement
Directional response to stimulus.	Response is generally not dependent on direction of stimulus.
Often associated with growth.	May occur through changes in turgor.
Usually relatively slow.	Some nastic movements can be rapid.
Example: Phototropism.	Example: Leaf folding in Mimosa.

19. Why Do Plants Need Coordination?

Plants need coordination to:

• Respond to environmental changes.
• Optimise growth towards favourable conditions.
• Obtain light and water.
• Respond to gravity.
• Protect themselves from certain environmental stresses.
• Coordinate growth, development and reproduction.

20. 30 MCQs – Multiple Choice Questions

Q1. Which system mainly coordinates activities in plants?

A) Nervous system only

B) Plant hormones and growth responses

C) Circulatory system

D) Skeletal system

Answer: B

Q2. Growth of a shoot towards light is called:

A) Geotropism

B) Hydrotropism

C) Phototropism

D) Chemotropism

Answer: C

Q3. Which hormone is strongly associated with phototropism?

A) Auxin

B) ABA

C) Ethylene

D) Cytokinin

Answer: A

Q4. Auxin is mainly produced in:

A) Root hairs only

B) Shoot tips

C) Fruits only

D) Xylem only

Answer: B

Q5. Roots generally show positive:

A) Phototropism

B) Geotropism

C) Thigmotropism

D) Negative hydrotropism

Answer: B

Q6. Roots generally grow towards water due to:

A) Hydrotropism

B) Phototropism

C) Chemotropism

D) Thermotropism

Answer: A

Q7. Tendrils coiling around support demonstrate:

A) Phototropism

B) Hydrotropism

C) Thigmotropism

D) Geotropism

Answer: C

Q8. Pollen tube growth towards ovule is commonly associated with:

A) Geotropism

B) Chemotropism

C) Phototropism

D) Hydrotropism

Answer: B

Q9. Which hormone promotes cell division?

A) Cytokinin

B) ABA

C) Ethylene

D) Auxin

Answer: A

Q10. Which hormone promotes stem elongation?

A) ABA

B) Cytokinin

C) Gibberellin

D) Ethylene

Answer: C

Q11. Which hormone generally inhibits growth?

A) Auxin

B) Gibberellin

C) Cytokinin

D) Abscisic acid

Answer: D

Q12. Which plant hormone is gaseous?

A) Auxin

B) Ethylene

C) Cytokinin

D) ABA

Answer: B

Q13. Fruit ripening is promoted by:

A) Ethylene

B) ABA

C) Cytokinin

D) Auxin

Answer: A

Q14. Which hormone helps promote dormancy in seeds?

A) Auxin

B) ABA

C) Ethylene

D) Gibberellin

Answer: B

Q15. A shoot growing towards light is an example of:

A) Positive phototropism

B) Negative phototropism

C) Positive geotropism

D) Negative hydrotropism

Answer: A

Q16. Growth away from gravity by shoot is:

A) Positive geotropism

B) Negative geotropism

C) Positive hydrotropism

D) Chemotropism

Answer: B

Q17. Which movement is caused mainly by unequal growth?

A) Phototropic bending

B) Leaf folding in Mimosa

C) Sleep movement only

D) Turgor movement only

Answer: A

Q18. Mimosa leaves fold when touched mainly because of:

A) Unequal DNA replication

B) Changes in turgor/water content

C) Cell division

D) Photosynthesis

Answer: B

Q19. Which stimulus causes geotropism?

A) Light

B) Water

C) Gravity

D) Touch

Answer: C

Q20. Which stimulus causes hydrotropism?

A) Gravity

B) Water

C) Light

D) Sound

Answer: B

Q21. Which is a positive tropic response?

A) Shoot away from light

B) Root away from water

C) Root towards water

D) Shoot away from gravity

Answer: C

Q22. Which hormone is associated with growth inhibition and stress response?

A) ABA

B) Auxin

C) Cytokinin

D) Gibberellin

Answer: A

Q23. Which hormone is especially associated with cell division?

A) Ethylene

B) Cytokinin

C) ABA

D) Auxin

Answer: B

Q24. Which hormone is associated with stem elongation?

A) Gibberellin

B) ABA

C) Ethylene

D) Cytokinin

Answer: A

Q25. Directional growth in response to touch is called:

A) Phototropism

B) Geotropism

C) Thigmotropism

D) Hydrotropism

Answer: C

Q26. Which pair is correctly matched?

A) Ethylene – fruit ripening

B) ABA – cell division

C) Cytokinin – growth inhibition

D) Auxin – fruit ripening only

Answer: A

Q27. Which plant part generally shows positive geotropism?

A) Shoot

B) Root

C) Flower only

D) Leaf only

Answer: B

Q28. Plants coordinate their responses mainly without:

A) Hormones

B) Growth changes

C) Nervous system like animals

D) Cellular responses

Answer: C

Q29. Which is NOT a tropic movement?

A) Phototropism

B) Geotropism

C) Hydrotropism

D) Leaf folding in Mimosa due to touch

Answer: D

Q30. Correct sequence in phototropic bending is:

A) Light → Auxin redistribution → Unequal growth → Bending

B) Light → Ethylene → Cell death → Bending

C) Gravity → Cytokinin → Bending

D) Water → ABA → Bending

Answer: A

21. 2 Marks Questions – 2 अंक

2 Marks Q1. What is coordination in plants?

Coordination in plants is the regulation of different activities and responses so that the plant can respond appropriately to environmental stimuli.

2 Marks Q2. What are plant hormones?

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

2 Marks Q3. Define phototropism.

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

2 Marks Q4. What is hydrotropism?

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

2 Marks Q5. Name two plant hormones.

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

22. 3 Marks Questions – 3 अंक

3 Marks Q6. Explain positive and negative phototropism.

Positive phototropism is growth towards light, as shown by shoots. Negative phototropism is growth away from light, commonly shown by roots.

3 Marks Q7. Explain geotropism with examples.

Geotropism is growth in response to gravity. Roots show positive geotropism by growing in the direction of gravity, while shoots generally show negative geotropism.

3 Marks Q8. What is the role of auxin in phototropism?

Light causes auxin to redistribute towards the shaded side of the shoot. Cells on that side elongate more, causing the shoot to bend towards light.

3 Marks Q9. Name three types of tropic movements.

Phototropism, geotropism and hydrotropism. Thigmotropism and chemotropism are other examples.

3 Marks Q10. Write the functions of auxin, cytokinin and gibberellin.

Auxin promotes cell elongation and phototropic responses. Cytokinin promotes cell division. Gibberellin promotes stem elongation and growth.

23. 4 Marks Questions – 4 अंक

4 Marks Q11. Explain four types of tropic movements.

1. Phototropism – response to light.
2. Geotropism – response to gravity.
3. Hydrotropism – response to water.
4. Thigmotropism – response to touch.

4 Marks Q12. Explain the role of auxin in shoot phototropism.

Auxin is produced mainly in shoot tips. When light falls from one side, auxin redistributes towards the shaded side. Cells there elongate more, resulting in unequal growth and bending of the shoot towards light.

4 Marks Q13. Differentiate between tropic and nastic movements.

Tropic movements are directional responses to stimuli and are often growth-dependent. Nastic movements generally do not depend on the direction of stimulus and may result from changes in turgor. Phototropism is a tropic movement, while Mimosa leaf folding is a nastic movement.

4 Marks Q14. Write four important plant hormones and their functions.

Auxin – cell elongation and phototropism.
Gibberellin – stem elongation.
Cytokinin – cell division.
ABA – growth inhibition, dormancy and stress response.

4 Marks Q15. Explain hydrotropism and thigmotropism with examples.

Hydrotropism is directional growth in response to water; roots generally grow towards water. Thigmotropism is directional growth in response to touch; tendrils of climbing plants coil around supports.

24. 5 Marks Questions – 5 अंक

5 Marks Q16. Explain coordination in plants.

Plants do not possess a nervous system like animals. They coordinate activities through plant hormones, growth responses and cellular changes. They respond to light, gravity, water, touch and chemicals. Tropic movements such as phototropism and geotropism help plants respond directionally to environmental stimuli.

5 Marks Q17. Explain phototropism with the role of auxin.

Phototropism is directional growth in response to light. In a shoot receiving light from one side, auxin redistributes towards the shaded side. Cells on the shaded side elongate more. This unequal growth causes the shoot to bend towards the light source.

5 Marks Q18. Explain five major plant hormones.

1. Auxin – cell elongation and phototropism.
2. Gibberellin – stem elongation and growth.
3. Cytokinin – cell division.
4. ABA – growth inhibition, dormancy and stress response.
5. Ethylene – fruit ripening and other developmental responses.

5 Marks Q19. Explain different types of tropic movements.

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

5 Marks Q20. Differentiate between plant coordination and animal coordination.

Animals possess specialised nervous systems and endocrine systems for rapid and coordinated responses. Plants do not have a nervous system like animals. Plants mainly use hormones, growth responses, cellular signalling and changes in turgor to coordinate activities.

25. 6 Marks Questions – 6 अंक

6 Marks Q21. Explain the complete mechanism of phototropism.

1. Light falls on one side of the shoot.
2. The plant detects the directional light stimulus.
3. Auxin becomes unevenly distributed in the shoot.
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 light.

6 Marks Q22. Explain the five major plant hormones with their functions.

Auxin: Promotes cell elongation and phototropic growth.

Gibberellin: Promotes stem elongation and growth.

Cytokinin: Promotes cell division.

ABA: Inhibits growth, promotes dormancy and helps in stress responses.

Ethylene: Promotes fruit ripening and influences several developmental processes.

6 Marks Q23. Explain different tropic movements with examples.

Phototropism: Growth in response to light; shoot grows towards light.

Geotropism: Growth in response to gravity; roots show positive response.

Hydrotropism: Growth in response to water; roots grow towards moisture.

Thigmotropism: Growth in response to touch; tendrils coil around support.

Chemotropism: Growth in response to chemicals; pollen tube grows towards ovule.

6 Marks Q24. Compare tropic and nastic movements.

Tropic Movement	Nastic Movement
Directional response to stimulus.	Usually independent of direction of stimulus.
Often caused by differential growth.	May result from changes in turgor.
Generally slower.	Some can be rapid.
Example: phototropism.	Example: Mimosa leaf folding.

6 Marks Q25. Explain the importance of plant hormones in coordination.

Plant hormones regulate growth, development and responses. Auxin helps in cell elongation and phototropism. Gibberellin promotes stem growth. Cytokinin promotes cell division. ABA inhibits growth, promotes dormancy and helps in stress responses. Ethylene promotes fruit ripening. Thus, hormones coordinate many plant activities.

6 Marks Q26. Explain how plants respond to different environmental stimuli.

Plants respond to light through phototropism, gravity through geotropism, water through hydrotropism, touch through thigmotropism and chemicals through chemotropism. These responses may involve plant hormones, differential growth or changes in cellular water/turgor.

6 Marks Q27. Explain the response of Mimosa pudica to touch.

When Mimosa leaves are touched, they fold or droop rapidly. This movement is not primarily caused by growth. It results from changes in water content and turgor pressure in specialised cells. It is therefore different from slow growth-dependent movements such as phototropism.

6 Marks Q28. Why do roots and shoots respond differently to gravity?

Roots generally grow in the direction of gravity and therefore show positive geotropism. Shoots generally grow opposite to gravity and show negative geotropism. Their different growth responses result from the way growth-regulating mechanisms operate in their respective tissues.

6 Marks Q29. Explain how plants coordinate without a nervous system.

Plants do not possess a nervous system like animals. They use chemical messengers such as plant hormones and local cellular signalling. Growth changes, differential cell elongation and changes in turgor also help produce responses. Thus, plants coordinate their activities through chemical and cellular mechanisms.

6 Marks Q30. Draw and explain a labelled diagram of phototropism.

The diagram should show:

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

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

26. HOTS / Competency Based Questions

HOTS 1: A plant is kept near a window and its shoot bends towards the window. Why?

The shoot receives light mainly from one direction. Auxin redistribution causes greater cell elongation on the shaded side, resulting in bending towards the light.

HOTS 2: A root is growing towards a moist region of soil. Which response is involved?

Positive hydrotropism.

HOTS 3: Why is Mimosa leaf folding different from phototropism?

Phototropism is a directional growth response, whereas Mimosa leaf folding mainly results from rapid changes in turgor/water content rather than growth.

HOTS 4: Which hormone would you associate with fruit ripening?

Ethylene.

27. CBSE Golden Points – परीक्षा के लिए महत्वपूर्ण

⭐ Point 1: Plants do not have a nervous system like animals.

⭐ Point 2: Plant coordination mainly involves hormones, growth and cellular responses.

⭐ Point 3: Auxin → Cell elongation + Phototropism.

⭐ Point 4: Gibberellin → Stem elongation.

⭐ Point 5: Cytokinin → Cell division.

⭐ Point 6: ABA → Growth inhibition + Dormancy + Stress response.

⭐ Point 7: Ethylene → Fruit ripening.

⭐ Point 8: Phototropism → Light.

⭐ Point 9: Geotropism → Gravity.

⭐ Point 10: Hydrotropism → Water.

⭐ Point 11: Thigmotropism → Touch.

⭐ Point 12: Chemotropism → Chemical stimulus.

⭐ Point 13: Shoot → Positive phototropism.

⭐ Point 14: Root → Positive geotropism and positive hydrotropism.

⭐ Point 15: Mimosa leaf folding → Turgor-based movement, not growth.

28. Quick Revision Table

Term	One-Line Revision
Auxin	Cell elongation and phototropism
Gibberellin	Stem elongation
Cytokinin	Cell division
ABA	Growth inhibition, dormancy, stress response
Ethylene	Fruit ripening
Phototropism	Response to light
Geotropism	Response to gravity
Hydrotropism	Response to water
Thigmotropism	Response to touch
Chemotropism	Response to chemicals

29. 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

30. Super-Fast Memory Trick

AUXIN = ELONGATION + PHOTOTROPISM

GIBBERELLIN = HEIGHT / STEM GROWTH

CYTOKININ = CELL DIVISION

ABA = BRAKE + DORMANCY + STRESS

ETHYLENE = FRUIT RIPENING

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

Exam Tip: यदि प्रश्न में “shoot bends towards light” आए तो Positive Phototropism + Auxin याद रखें। यदि “root grows towards water” आए तो Positive Hydrotropism और यदि “tendril coils around support” आए तो Thigmotropism लिखें।