🌿 Control and Coordination
Tropic Movements in Plants | पादपों में अनुवर्ती गतियाँ | Class 10 Science | CBSE + Foundation + Competitive
🌱 Tropic Movements in Plants
1. Tropic Movements – अनुवर्ती गतियाँ
Tropic movement is the directional growth movement of a plant part in response to an external stimulus.
अनुवर्ती गति वह दिशात्मक वृद्धि गति है जिसमें पौधे का कोई भाग किसी बाहरी उद्दीपन के प्रति एक निश्चित दिशा में वृद्धि करता है।
The direction of movement depends upon the direction of the stimulus.
Examples:
अनुवर्ती गति वह दिशात्मक वृद्धि गति है जिसमें पौधे का कोई भाग किसी बाहरी उद्दीपन के प्रति एक निश्चित दिशा में वृद्धि करता है।
The direction of movement depends upon the direction of the stimulus.
Examples:
- Shoot bends towards light → Phototropism
- Root grows downward → Geotropism
- Root grows towards water → Hydrotropism
- Tendril coils around support → Thigmotropism
- Pollen tube grows towards ovule → Chemotropism
2. Important Types of Tropic Movements
☀️ Phototropism
Response to light
प्रकाश
🌍 Geotropism
Response to gravity
गुरुत्व
💧 Hydrotropism
Response to water
जल
🤝 Thigmotropism
Response to touch
स्पर्श
🧪 Chemotropism
Response to chemicals
रसायन
3. Phototropism – प्रकाशानुवर्तन
Phototropism is the directional growth of a plant part in response to light.
प्रकाश की दिशा के अनुसार पौधे के किसी भाग की वृद्धि को प्रकाशानुवर्तन (Phototropism) कहते हैं।
Positive phototropism: Growth towards light.
Negative phototropism: Growth away from light.
The shoot generally shows positive phototropism.
प्रकाश की दिशा के अनुसार पौधे के किसी भाग की वृद्धि को प्रकाशानुवर्तन (Phototropism) कहते हैं।
Positive phototropism: Growth towards light.
Negative phototropism: Growth away from light.
The shoot generally shows positive phototropism.
☀️ Animated Diagram – Phototropism in Shoot
Light → Auxin redistribution → Unequal growth → Shoot bends towards light
4. Role of Auxin in Phototropism
When light falls from one side of a shoot:
यदि प्रकाश केवल एक तरफ से आता है तो ऑक्सिन के असमान वितरण के कारण shaded side की कोशिकाओं में अधिक elongation होता है और shoot प्रकाश की ओर मुड़ता है।
- Light is detected by the growing shoot.
- Auxin is redistributed within the shoot.
- In a typical shoot response, more auxin accumulates on the shaded side.
- Cells on the shaded side elongate more.
- This produces differential growth.
- The shoot bends towards the light.
यदि प्रकाश केवल एक तरफ से आता है तो ऑक्सिन के असमान वितरण के कारण shaded side की कोशिकाओं में अधिक elongation होता है और shoot प्रकाश की ओर मुड़ता है।
5. Geotropism / Gravitropism – गुरुत्वानुवर्तन
The directional growth response of a plant part to gravity is called geotropism or gravitropism.
गुरुत्वाकर्षण के प्रति पौधे के भाग की दिशात्मक वृद्धि को गुरुत्वानुवर्तन कहते हैं।
Root: Positive geotropism.
Shoot: Negative geotropism.
गुरुत्वाकर्षण के प्रति पौधे के भाग की दिशात्मक वृद्धि को गुरुत्वानुवर्तन कहते हैं।
Root: Positive geotropism.
Shoot: Negative geotropism.
🌍 Animated Diagram – Geotropism
Root → Positive Geotropism
Shoot → Negative Geotropism
Shoot → Negative Geotropism
6. Hydrotropism – जलानुवर्तन
Hydrotropism is the directional growth response of a plant part to water or moisture.
जल या नमी की दिशा में पौधे की वृद्धि को जलानुवर्तन कहते हैं।
Roots generally grow towards a region with greater moisture.
Therefore, roots generally show positive hydrotropism.
जल या नमी की दिशा में पौधे की वृद्धि को जलानुवर्तन कहते हैं।
Roots generally grow towards a region with greater moisture.
Therefore, roots generally show positive hydrotropism.
💧 Animated Diagram – Hydrotropism
7. Thigmotropism – स्पर्शानुवर्तन
Thigmotropism is the directional growth response of a plant part to touch or contact.
स्पर्श या संपर्क के कारण पौधे के किसी भाग की दिशात्मक वृद्धि को स्पर्शानुवर्तन कहते हैं।
Example: Tendrils of climbing plants coil around a support.
This movement helps climbing plants obtain mechanical support.
स्पर्श या संपर्क के कारण पौधे के किसी भाग की दिशात्मक वृद्धि को स्पर्शानुवर्तन कहते हैं।
Example: Tendrils of climbing plants coil around a support.
This movement helps climbing plants obtain mechanical support.
🤝 Animated Diagram – Tendril and Support
8. Chemotropism – रसायनानुवर्तन
Chemotropism is the directional growth response of a plant part to a chemical stimulus.
रासायनिक पदार्थों के प्रति पौधे के किसी भाग की दिशात्मक वृद्धि को रसायनानुवर्तन कहते हैं।
Important example: The pollen tube grows towards the ovule due to chemical signals.
यह उदाहरण पौधों में प्रजनन एवं रासायनिक संकेतों के समन्वय को दर्शाता है।
रासायनिक पदार्थों के प्रति पौधे के किसी भाग की दिशात्मक वृद्धि को रसायनानुवर्तन कहते हैं।
Important example: The pollen tube grows towards the ovule due to chemical signals.
यह उदाहरण पौधों में प्रजनन एवं रासायनिक संकेतों के समन्वय को दर्शाता है।
🧪 Animated Diagram – Chemotropism in Pollen Tube
9. Positive and Negative Tropism
Positive tropism: Growth towards the stimulus.
Negative tropism: Growth away from the stimulus.
Examples:
Negative tropism: Growth away from the stimulus.
Examples:
- Shoot towards light → Positive phototropism
- Root towards gravity → Positive geotropism
- Shoot away from gravity → Negative geotropism
- Root towards water → Positive hydrotropism
10. Complete Comparison Table
| Type | Stimulus | Positive Response | Example |
|---|---|---|---|
| Phototropism | Light | Growth towards light | Shoot bends towards light |
| Geotropism | Gravity | Growth towards gravity | Root grows downward |
| Hydrotropism | Water | Growth towards water | Root grows towards moisture |
| Thigmotropism | Touch | Growth towards/contact with support | Tendril coils around support |
| Chemotropism | Chemicals | Growth towards chemical signal | Pollen tube towards ovule |
11. Tropic vs Nastic Movement
| Tropic Movement | Nastic Movement |
|---|---|
| Directional response. | Generally independent of stimulus direction. |
| Often related to differential growth. | May occur due to turgor changes. |
| Usually relatively slow. | Some responses are rapid. |
| Example: Phototropism. | Example: Mimosa leaf folding. |
12. 30 MCQs – Multiple Choice Questions
Q1. What is tropic movement?
A) Directional growth response to a stimulus
B) Random movement
C) Movement of animals
D) Movement caused only by water
Answer: A
Q2. Phototropism is a response to:
A) Gravity
B) Light
C) Water
D) Touch
Answer: B
Q3. Root growth towards gravity is:
A) Negative phototropism
B) Hydrotropism
C) Positive geotropism
D) Chemotropism
Answer: C
Q4. Tendril coiling around a support is:
A) Phototropism
B) Geotropism
C) Hydrotropism
D) Thigmotropism
Answer: D
Q5. Which hormone plays an important role in phototropism?
A) Auxin
B) Ethylene
C) ABA
D) Cytokinin
Answer: A
Q6. Roots generally show positive:
A) Phototropism
B) Hydrotropism
C) Chemotropism only
D) Negative geotropism
Answer: B
Q7. Chemotropism is a response to:
A) Light
B) Gravity
C) Chemical stimulus
D) Touch
Answer: C
Q8. Pollen tube growth towards the ovule is an example of:
A) Geotropism
B) Hydrotropism
C) Phototropism
D) Chemotropism
Answer: D
Q9. A shoot bending towards light is:
A) Positive phototropism
B) Negative phototropism
C) Positive geotropism
D) Negative hydrotropism
Answer: A
Q10. A shoot generally shows:
A) Positive geotropism
B) Negative geotropism
C) Positive hydrotropism
D) Positive chemotropism
Answer: B
Q11. The stimulus in thigmotropism is:
A) Water
B) Gravity
C) Touch
D) Light
Answer: C
Q12. The stimulus in hydrotropism is:
A) Gravity
B) Light
C) Touch
D) Water
Answer: D
Q13. Which plant part commonly shows positive phototropism?
A) Shoot
B) Root
C) Seed coat
D) Fruit
Answer: A
Q14. Which plant part commonly shows positive geotropism?
A) Leaf
B) Root
C) Flower
D) Fruit
Answer: B
Q15. Unequal growth of shoot cells during phototropism is mainly related to:
A) Ethylene
B) ABA
C) Auxin
D) Cytokinin
Answer: C
Q16. Growth away from a stimulus is called:
A) Positive tropism
B) Nastic movement
C) Random movement
D) Negative tropism
Answer: D
Q17. Which is NOT a tropic movement?
A) Folding of Mimosa leaves
B) Phototropism
C) Geotropism
D) Hydrotropism
Answer: A
Q18. Root growth towards a moist region demonstrates:
A) Thigmotropism
B) Hydrotropism
C) Phototropism
D) Chemotropism
Answer: B
Q19. A tendril responds mainly to:
A) Gravity
B) Light
C) Touch
D) Water
Answer: C
Q20. Pollen tube is attracted towards the ovule by:
A) Gravity
B) Light
C) Water
D) Chemical signals
Answer: D
Q21. Which statement is correct?
A) Roots generally show positive geotropism
B) Shoots generally show positive geotropism
C) Roots always grow away from water
D) Shoots never respond to light
Answer: A
Q22. Which movement is directional?
A) Nastic movement
B) Tropic movement
C) Random movement
D) All movements are non-directional
Answer: B
Q23. Phototropism is generally caused by:
A) Equal growth on both sides
B) No growth
C) Differential growth
D) Only cell death
Answer: C
Q24. Which pair is correctly matched?
A) Phototropism – Gravity
B) Geotropism – Water
C) Hydrotropism – Touch
D) Chemotropism – Chemical
Answer: D
Q25. Which hormone is mainly associated with cell elongation?
A) Auxin
B) ABA
C) Ethylene
D) Cytokinin
Answer: A
Q26. Negative geotropism is shown by:
A) Root
B) Shoot
C) Root hair
D) Ovule
Answer: B
Q27. Which tropism helps climbing plants obtain support?
A) Hydrotropism
B) Chemotropism
C) Thigmotropism
D) Geotropism
Answer: C
Q28. Which is the correct sequence in shoot phototropism?
A) Light → Cell death → Bending
B) Water → ABA → Bending
C) Touch → Cytokinin → Bending
D) Light → Auxin redistribution → Differential growth → Bending
Answer: D
Q29. Growth towards a stimulus is called:
A) Positive tropism
B) Negative tropism
C) Random movement
D) Nastic movement
Answer: A
Q30. Which one is correctly matched?
A) Thigmotropism – Water
B) Hydrotropism – Water
C) Phototropism – Gravity
D) Geotropism – Chemical
Answer: B
13. 2 Marks Questions – 2 अंक
2 Marks
Q1. Define tropic movement.
Tropic movement is the directional growth response of a plant part to an external stimulus.
2 Marks
Q2. What is phototropism?
Phototropism is the directional growth response of a plant part to light.
2 Marks
Q3. Define geotropism.
Geotropism is the directional growth response of a plant to gravity.
2 Marks
Q4. What is hydrotropism?
Hydrotropism is the directional growth response to water or moisture.
2 Marks
Q5. Give one example of thigmotropism.
Coiling of tendrils around a support is an example of thigmotropism.
14. 3 Marks Questions – 3 अंक
3 Marks
Q6. Differentiate between positive and negative tropism.
Positive tropism is growth towards the stimulus, whereas negative tropism is growth away from the stimulus.
3 Marks
Q7. Write three examples of tropic movements.
Shoot towards light – phototropism; root towards gravity – geotropism; root towards water – hydrotropism.
3 Marks
Q8. What is the role of auxin in phototropism?
Auxin becomes unevenly distributed in a shoot receiving light from one side. Greater auxin accumulation on the shaded side promotes greater elongation there, causing the shoot to bend towards light.
3 Marks
Q9. Explain thigmotropism with an example.
Thigmotropism is directional growth in response to touch. Tendrils of climbing plants coil around a support after coming into contact with it.
3 Marks
Q10. Explain chemotropism with an example.
Chemotropism is directional growth in response to a chemical stimulus. The pollen tube grows towards the ovule in response to chemical signals.
15. 4 Marks Questions – 4 अंक
4 Marks
Q11. Explain phototropism in a plant shoot.
Light from one side causes redistribution of auxin in the shoot. More auxin accumulates on the shaded side. Cells on the shaded side elongate more, resulting in differential growth. Hence the shoot bends towards light.
4 Marks
Q12. Explain positive and negative geotropism.
Root growth in the direction of gravity is positive geotropism. Shoot growth opposite to the direction of gravity is negative geotropism.
4 Marks
Q13. Explain hydrotropism.
Hydrotropism is the directional growth response to water or moisture. Roots generally grow towards regions containing more moisture and therefore commonly show positive hydrotropism.
4 Marks
Q14. Write four types of tropic movements with their stimuli.
Phototropism – light.
Geotropism – gravity.
Hydrotropism – water.
Thigmotropism – touch.
Geotropism – gravity.
Hydrotropism – water.
Thigmotropism – touch.
4 Marks
Q15. Differentiate between tropic and nastic movements.
Tropic movement is directional and is often associated with growth. Nastic movement generally does not depend on the direction of the stimulus and may result from turgor changes. Phototropism is tropic, while Mimosa leaf folding is nastic.
16. 5 Marks Questions – 5 अंक
5 Marks
Q16. Explain the 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
Q17. Explain the mechanism of phototropism.
Light falls on one side of the shoot. Auxin is redistributed, with greater accumulation on the shaded side in a typical shoot response. The shaded-side cells elongate more. Differential growth develops and the shoot bends towards the light.
5 Marks
Q18. Explain the importance of tropic movements in plants.
Tropic movements help plants respond appropriately to their surroundings. Phototropism helps shoots obtain light, hydrotropism helps roots reach water, geotropism establishes proper orientation, thigmotropism helps climbing plants obtain support and chemotropism helps reproductive growth such as pollen tube growth towards the ovule.
5 Marks
Q19. Explain positive and negative tropism with examples.
Positive tropism means growth towards the stimulus. Example: shoot towards light and root towards gravity. Negative tropism means growth away from the stimulus. Example: shoot growing opposite to gravity.
5 Marks
Q20. Explain the role of auxin in plant movement.
Auxin regulates cell elongation and differential growth. In phototropism, unequal distribution of auxin in the shoot causes one side to elongate more than the other. This unequal growth results in bending of the shoot towards light.
17. 6 Marks Questions – 6 अंक
6 Marks
Q21. Explain phototropism, geotropism and hydrotropism with examples.
Phototropism: Directional growth in response to light. Shoots generally grow towards light.
Geotropism: Directional growth in response to gravity. Roots generally grow in the direction of gravity.
Hydrotropism: Directional growth in response to water. Roots generally grow towards moisture.
Geotropism: Directional growth in response to gravity. Roots generally grow in the direction of gravity.
Hydrotropism: Directional growth in response to water. Roots generally grow towards moisture.
6 Marks
Q22. Explain five types of tropic movements.
1. Phototropism: Response to light.
2. Geotropism: Response to gravity.
3. Hydrotropism: Response to water.
4. Thigmotropism: Response to touch.
5. Chemotropism: Response to chemicals.
2. Geotropism: Response to gravity.
3. Hydrotropism: Response to water.
4. Thigmotropism: Response to touch.
5. Chemotropism: Response to chemicals.
6 Marks
Q23. Describe the role of auxin in bending of a shoot towards light.
Light from one side causes redistribution of auxin in the shoot. More auxin accumulates on the shaded side. Cells on that side elongate more. This produces unequal growth between the two sides of the shoot. As a result, the shoot bends towards the light.
6 Marks
Q24. Explain positive and negative tropic responses in roots and shoots.
Roots generally show positive geotropism because they grow towards gravity. Shoots generally show negative geotropism because they grow away from gravity. Shoots generally show positive phototropism because they grow towards light. Roots generally show positive hydrotropism because they grow towards moisture.
6 Marks
Q25. Explain thigmotropism and chemotropism in detail.
Thigmotropism is directional growth caused by touch. Tendrils of climbing plants coil around a support and help the plant climb.
Chemotropism is directional growth caused by chemical stimuli. A pollen tube grows towards the ovule under the influence of chemical signals.
Chemotropism is directional growth caused by chemical stimuli. A pollen tube grows towards the ovule under the influence of chemical signals.
6 Marks
Q26. Differentiate between the five major tropic movements.
| Movement | Stimulus | Example |
|---|---|---|
| Phototropism | Light | Shoot towards light |
| Geotropism | Gravity | Root grows downward |
| Hydrotropism | Water | Root towards moisture |
| Thigmotropism | Touch | Tendril around support |
| Chemotropism | Chemicals | Pollen tube towards ovule |
6 Marks
Q27. Explain how tropic movements help plants survive.
Plants cannot move from one place to another like animals, so directional growth responses help them adjust to environmental conditions. Shoots grow towards light, roots grow towards gravity and moisture, tendrils obtain support and pollen tubes respond to chemical signals. These coordinated responses help growth, nutrition, support and reproduction.
6 Marks
Q28. Explain tropic movement with a suitable diagram of phototropism.
The diagram should show a shoot receiving light from one side, auxin redistribution, greater elongation on the shaded side and bending towards the light.
Sequence:
Light → Auxin redistribution → Unequal elongation → Bending towards light.
Sequence:
Light → Auxin redistribution → Unequal elongation → Bending towards light.
6 Marks
Q29. Compare phototropism, geotropism and hydrotropism.
| Feature | Phototropism | Geotropism | Hydrotropism |
|---|---|---|---|
| Stimulus | Light | Gravity | Water |
| Common example | Shoot | Root | Root |
| Positive response | Towards light | Towards gravity | Towards water |
6 Marks
Q30. How do plant hormones and tropic movements work together in coordination?
Plant hormones act as chemical messengers that regulate growth and development. Auxin is particularly important in differential growth during phototropism. The stimulus causes changes in hormone distribution or activity, leading to unequal growth of plant parts. Tropic movements therefore provide a coordinated response to light, gravity, water, touch and chemical signals.
18. HOTS / Competency Based Questions
HOTS 1: A plant kept near a window bends towards the window. Why?
Because light comes mainly from one direction. Auxin redistribution causes greater elongation on the shaded side, producing bending towards the light.
HOTS 2: A root grows towards a moist region of soil. Which tropism is involved?
Positive hydrotropism.
HOTS 3: Why does a climbing plant coil around a support?
Because its tendril responds to touch and shows thigmotropism.
HOTS 4: A pollen tube grows towards an ovule. Which stimulus is responsible?
Chemical signals; therefore the movement is chemotropism.
19. CBSE Golden Points – परीक्षा के लिए महत्वपूर्ण
⭐ Tropic movement = Directional growth response
⭐ Phototropism = Light
⭐ Geotropism = Gravity
⭐ Hydrotropism = Water
⭐ Thigmotropism = Touch
⭐ Chemotropism = Chemical stimulus
⭐ Shoot → Positive Phototropism
⭐ Root → Positive Geotropism
⭐ Shoot → Negative Geotropism
⭐ Root → Positive Hydrotropism
⭐ Tendril → Thigmotropism
⭐ Pollen tube → Chemotropism
⭐ Auxin → Cell elongation + Phototropism
⭐ Phototropism = Light
⭐ Geotropism = Gravity
⭐ Hydrotropism = Water
⭐ Thigmotropism = Touch
⭐ Chemotropism = Chemical stimulus
⭐ Shoot → Positive Phototropism
⭐ Root → Positive Geotropism
⭐ Shoot → Negative Geotropism
⭐ Root → Positive Hydrotropism
⭐ Tendril → Thigmotropism
⭐ Pollen tube → Chemotropism
⭐ Auxin → Cell elongation + Phototropism
20. One-Line Revision
| Question | Answer |
|---|---|
| Movement towards light? | Phototropism |
| Movement due to gravity? | Geotropism |
| Movement towards water? | Hydrotropism |
| Movement due to touch? | Thigmotropism |
| Movement due to chemical? | Chemotropism |
| Root towards gravity? | Positive geotropism |
| Shoot towards light? | Positive phototropism |
| Shoot away from gravity? | Negative geotropism |
| Root towards water? | Positive hydrotropism |
| Tendril around support? | Thigmotropism |
| Pollen tube towards ovule? | Chemotropism |
| Important hormone in phototropism? | Auxin |
21. Diagram Labelling Practice
CBSE परीक्षा में निम्न diagrams की practice करें:
- Phototropism in shoot
- Role of auxin in phototropism
- Positive and negative geotropism
- Hydrotropism in roots
- Thigmotropism in tendrils
- Chemotropism in pollen tube
22. Super Memory Trick
PHOTO = LIGHT ☀️
GEO = GRAVITY 🌍
HYDRO = WATER 💧
THIGMO = TOUCH 🤝
CHEMO = CHEMICAL 🧪
AUXIN = ELONGATION + PHOTOTROPISM
23. Final Exam Revision
Most Important Questions:
1. Define tropic movement.
2. Explain phototropism with diagram.
3. Explain the role of auxin in phototropism.
4. Define geotropism and explain positive and negative geotropism.
5. Explain hydrotropism with example.
6. Explain thigmotropism with example.
7. Explain chemotropism with example.
8. Differentiate positive and negative tropism.
9. Differentiate tropic and nastic movements.
10. Explain five types of tropic movements.
1. Define tropic movement.
2. Explain phototropism with diagram.
3. Explain the role of auxin in phototropism.
4. Define geotropism and explain positive and negative geotropism.
5. Explain hydrotropism with example.
6. Explain thigmotropism with example.
7. Explain chemotropism with example.
8. Differentiate positive and negative tropism.
9. Differentiate tropic and nastic movements.
10. Explain five types of tropic movements.
