These NCERT Notes on Coordination in Plants provide a clear and concise explanation of how plants respond to internal and external stimuli through plant hormones and various movements. The notes are specially designed for Class 10 and Class 11 Biology students, as well as NEET, CUET, and other competitive exam aspirants following the NCERT syllabus. Written in a simple, concept-based, and exam-oriented style, these notes help students understand the topic thoroughly and revise it quickly before examinations.
Plants do not have a nervous system like animals, yet they are able to respond to different environmental changes. The process through which different parts of a plant work together and show suitable responses to internal and external stimuli is called Coordination in Plants (पादपों में समन्वय).
According to NCERT, coordination in plants mainly occurs through:
- Immediate movements (Tropic and Nastic movements)
- Chemical coordination through Plant Hormones
What is Coordination in Plants?
Coordination is the process by which plants receive stimuli and produce an appropriate response.
Stimulus (उद्दीपन)
Any change in surroundings that causes a reaction.
Examples:
- Light
- Water
- Gravity
- Touch
- Chemicals
Response
The action shown by the plant after receiving a stimulus.
Example:
- Plant bends toward sunlight.
Why Do Plants Need Coordination?
Plants require coordination for:
- Growth and development
- Survival in changing environment
- Obtaining sunlight
- Absorbing water and minerals
- Protection from harmful conditions
- Reproduction
Characteristics of Coordination in Plants
| Characteristic | Description |
|---|---|
| No nervous system | Plants coordinate without nerves |
| Chemical control | Mainly controlled by hormones |
| Slow response | Responses are slower than animals |
| Stimulus-based | Responses occur due to environmental changes |
Types of Coordination in Plants
Plants coordinate mainly through two mechanisms:
1. Movement-Based Coordination
Movement in plants occurs as a response to stimuli.
Two major categories:
A. Tropic Movements
Directional growth movement toward or away from stimulus.
B. Nastic Movements
Non-directional movement independent of stimulus direction.
Tropic Movements in Plants
Tropic movement is a directional movement of plant growth.
Types of Tropic Movements
| Type | Stimulus | Example |
|---|---|---|
| Phototropism | Light | Shoot bends toward light |
| Geotropism | Gravity | Roots grow downward |
| Hydrotropism | Water | Roots move toward water |
| Thigmotropism | Touch | Tendrils coil around support |
| Chemotropism | Chemicals | Pollen tube grows toward ovule |
1. Phototropism
Growth response to light.
Example:
- Stem bends toward sunlight.
Importance:
- Maximizes photosynthesis.
2. Geotropism
Growth response to gravity.
Types:
- Positive geotropism → roots
- Negative geotropism → shoots
3. Hydrotropism
Movement toward water.
Example:
Roots grow toward moist soil.
4. Thigmotropism
Movement due to touch.
Example:
Climbers wrap around support.
5. Chemotropism
Movement due to chemicals.
Example:
Pollen tube moves toward ovule.
Nastic Movements
These are movements that do not depend on stimulus direction.
Characteristics:
- Usually rapid
- Caused by changes in water pressure
Examples:
| Movement | Example |
|---|---|
| Seismonasty | Touch-me-not closes leaves |
| Photonasty | Flowers open in light |
Example: Mimosa pudica
Leaves fold when touched.
Reason:
- Rapid change in turgor pressure.
Chemical Coordination in Plants
Plants use hormones for internal coordination.
These hormones are produced in small quantities but control growth and responses.
These are called Plant Hormones (Phytohormones).
Major Plant Hormones
| Hormone | Main Function |
|---|---|
| Auxin | Cell elongation |
| Gibberellin | Stem growth |
| Cytokinin | Cell division |
| Abscisic Acid (ABA) | Growth inhibition |
| Ethylene | Fruit ripening |
1. Auxin
Functions:
- Promotes stem growth
- Causes phototropism
- Root initiation
Example:
Shoot bends toward light.
2. Gibberellins
Functions:
- Increase stem length
- Promote seed germination
3. Cytokinins
Functions:
- Cell division
- Delay aging
4. Abscisic Acid (ABA)
Functions:
- Growth inhibitor
- Causes dormancy
- Closes stomata
5. Ethylene
Functions:
- Fruit ripening
- Leaf fall
Coordination in Plants vs Coordination in Animals
| Basis | Plants | Animals |
|---|---|---|
| Control System | Hormones | Nervous + Endocrine |
| Speed | Slow | Fast |
| Movement | Growth-based | Muscular |
| Signal Type | Chemical | Electrical + Chemical |
Importance of Coordination in Plants
- Helps adaptation
- Supports reproduction
- Ensures proper growth
- Maintains survival
- Improves resource utilization
NCERT Important Points (Quick Revision)
- Plants respond to stimuli despite lacking nervous system.
- Tropic movements are directional.
- Nastic movements are non-directional.
- Hormones regulate plant growth.
- Auxin controls phototropism.
- ABA inhibits growth.
Practice Questions with Answers
Very Short Answer Questions
1. What is coordination in plants?
Answer: Process by which plants respond to stimuli.
2. Name one plant hormone.
Answer: Auxin.
3. Which movement occurs due to touch?
Answer: Thigmotropism.
4. Which hormone inhibits growth?
Answer: Abscisic Acid.
5. What causes phototropism?
Answer: Auxin.
Short Answer Questions
1. Explain tropic movement.
Answer: Directional growth movement of plants in response to stimuli.
2. Write functions of cytokinin.
Answer:
- Cell division
- Delays aging
3. Differentiate phototropism and geotropism.
| Phototropism | Geotropism |
|---|---|
| Response to light | Response to gravity |
Fill in the Blanks
- Plants coordinate mainly through ________.
Answer: hormones - Growth toward light is called ________.
Answer: phototropism - Root movement toward water is ________.
Answer: hydrotropism - ________ inhibits growth.
Answer: ABA - Ethylene helps in ________.
Answer: fruit ripening
MCQs (with Answers)
1. Coordination in plants occurs mainly through:
A. Nerves
B. Hormones
C. Bones
D. Muscles
Answer: B
2. Stem shows:
A. Positive phototropism
B. Negative phototropism
C. Hydrotropism
D. Chemotropism
Answer: A
3. Root grows downward due to:
A. Gravity
B. Light
C. Water
D. Air
Answer: A
4. Hormone responsible for fruit ripening:
A. Auxin
B. Cytokinin
C. Ethylene
D. ABA
Answer: C
5. Movement toward water:
A. Hydrotropism
B. Geotropism
C. Chemotropism
D. Photonasty
Answer: A
6. Plant coordination mainly depends on:
A. Blood
B. Hormones
C. Muscles
D. Brain
Answer: B
7. Mimosa shows:
A. Nastic movement
B. Tropic movement
C. Locomotion
D. Respiration
Answer: A
8. Cell division is promoted by:
A. Cytokinin
B. Auxin
C. ABA
D. Ethylene
Answer: A
9. Growth toward chemicals:
A. Chemotropism
B. Geotropism
C. Hydrotropism
D. Photonasty
Answer: A
10. Which is growth inhibitor?
A. Ethylene
B. Auxin
C. ABA
D. Cytokinin
Answer: C
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