Introduction
Pollination (परागण) is the process of transfer of pollen grains from the anther (पुंकेसर का परागकोष) to the stigma (वर्तिकाग्र) of a flower. It is an essential step in sexual reproduction in flowering plants. According to NCERT, pollination helps in fertilization and seed formation.
What is Pollination?
- Pollination is the transfer of pollen grains from anther to stigma.
- It occurs before fertilization.
- Pollination helps male gametes reach the female reproductive part of the flower.
- It is necessary for seed and fruit formation.
Importance of Pollination
- Ensures reproduction in flowering plants.
- Leads to fertilization.
- Helps in seed production.
- Maintains plant diversity.
- Increases crop yield in agricultural plants.
Types of Pollination
Pollination is mainly of two types:
| Type of Pollination | Definition |
|---|---|
| Self-Pollination | Transfer of pollen grains to the stigma of the same flower or another flower on the same plant |
| Cross-Pollination | Transfer of pollen grains from one plant to the flower of another plant of the same species |
1. Self-Pollination (स्व-परागण)
Self-pollination occurs when pollen grains are transferred from the anther to the stigma of the same flower or another flower on the same plant.
Characteristics of Self-Pollination
- Occurs within the same plant.
- Less dependence on external agents.
- Produces genetically similar offspring.
- Less wastage of pollen grains.
- Common in bisexual flowers.
Advantages of Self-Pollination
- Assured pollination.
- Maintains parental traits.
- Requires fewer pollen grains.
- Useful where pollinating agents are absent.
Disadvantages of Self-Pollination
- Little genetic variation.
- Reduced adaptability.
- May lead to weaker offspring over generations.
Examples
- Pea
- Wheat
- Rice
- Tomato
2. Cross-Pollination (पर-परागण)
Cross-pollination occurs when pollen grains are transferred from the anther of one plant to the stigma of a flower on another plant of the same species.
Characteristics of Cross-Pollination
- Occurs between different plants.
- Requires pollinating agents.
- Produces genetic variation.
- Enhances adaptability and survival.
Advantages of Cross-Pollination
- Creates genetic diversity.
- Produces healthier offspring.
- Increases resistance to diseases.
- Improves adaptability to environmental changes.
Disadvantages of Cross-Pollination
- Depends on external agents.
- More pollen grains are wasted.
- Pollination may fail if agents are absent.
Examples
- Maize
- Papaya
- Coconut
- Sunflower
Agents of Cross-Pollination
Cross-pollination is carried out by different agents.
| Agent | Example |
|---|---|
| Wind | Maize, Wheat, Grasses |
| Water | Vallisneria |
| Insects | Sunflower, Hibiscus |
| Birds | Some tropical flowers |
| Bats | Certain night-blooming flowers |
Comparison Between Self-Pollination and Cross-Pollination
| Feature | Self-Pollination | Cross-Pollination |
|---|---|---|
| Pollen Transfer | Same plant | Different plants |
| Need of Pollinating Agents | Usually not required | Required |
| Genetic Variation | Low | High |
| Pollen Wastage | Less | More |
| Adaptability | Lower | Higher |
| Offspring | Similar to parent | Diverse |
Significance of Cross-Pollination in Nature
- Promotes evolution.
- Maintains biodiversity.
- Produces stronger plant varieties.
- Improves agricultural productivity.
- Enhances disease resistance.
Key Points to Remember
- Pollination is the transfer of pollen grains from anther to stigma.
- Pollination occurs before fertilization.
- Pollination is of two main types: self-pollination and cross-pollination.
- Self-pollination occurs within the same plant.
- Cross-pollination occurs between different plants of the same species.
- Insects, wind, water, birds and bats act as pollinating agents.
- Cross-pollination promotes genetic variation.
Practice Questions
Very Short Answer Questions
1. What is pollination?
Answer: Pollination is the transfer of pollen grains from the anther to the stigma of a flower.
2. Name the two types of pollination.
Answer: Self-pollination and cross-pollination.
3. Which type of pollination produces genetic variation?
Answer: Cross-pollination.
4. Give one example of self-pollination.
Answer: Pea.
5. Give one example of cross-pollination.
Answer: Maize.
Short Answer Questions
1. Why is pollination important?
Answer:
- Helps in fertilization.
- Leads to seed formation.
- Ensures reproduction in flowering plants.
2. Mention two advantages of cross-pollination.
Answer:
- Produces genetic diversity.
- Creates healthier and more adaptable offspring.
3. What are pollinating agents?
Answer:
Pollinating agents are organisms or natural forces that transfer pollen grains from one flower to another, such as insects, wind and water.
Fill in the Blanks
- Pollination occurs before __________.
Answer: fertilization - Self-pollination occurs within the __________ plant.
Answer: same - Cross-pollination produces genetic __________.
Answer: variation - Bees are common pollinating __________.
Answer: insects - Pollen grains are produced in the __________.
Answer: anther - The stigma receives __________ grains.
Answer: pollen - Wind pollination is common in __________.
Answer: maize - Pollination is essential for __________ formation.
Answer: seed - Self-pollination causes less __________ of pollen.
Answer: wastage - Cross-pollination improves __________ diversity.
Answer: genetic
Multiple Choice Questions (MCQs)
1. Pollination is the transfer of pollen grains from:
A. Ovary to stigma
B. Anther to stigma
C. Stigma to ovary
D. Ovule to stigma
Answer: B. Anther to stigma
2. How many main types of pollination are there?
A. One
B. Two
C. Three
D. Four
Answer: B. Two
3. Self-pollination occurs in:
A. Different species
B. Same plant
C. Different plants only
D. Different families
Answer: B. Same plant
4. Which pollination produces genetic variation?
A. Self-pollination
B. Vegetative propagation
C. Cross-pollination
D. Budding
Answer: C. Cross-pollination
5. Which insect commonly helps in pollination?
A. Ant
B. Cockroach
C. Bee
D. Termite
Answer: C. Bee
6. Wind pollination is common in:
A. Rose
B. Maize
C. Lotus
D. Jasmine
Answer: B. Maize
7. Which part receives pollen grains?
A. Ovary
B. Style
C. Stigma
D. Sepal
Answer: C. Stigma
8. Which is an advantage of self-pollination?
A. High genetic variation
B. Less pollen wastage
C. Dependence on insects
D. More diversity
Answer: B. Less pollen wastage
9. Which is NOT a pollinating agent?
A. Wind
B. Water
C. Insects
D. Root
Answer: D. Root
10. Pollination is necessary for:
A. Respiration
B. Photosynthesis
C. Seed formation
D. Transpiration
Answer: C. Seed formation
Conclusion
Pollination is a vital biological process that enables sexual reproduction in flowering plants. The two main types of pollination are self-pollination and cross-pollination. While self-pollination ensures reproduction with less pollen wastage, cross-pollination promotes genetic diversity and healthier plant populations. Understanding these types helps students learn the foundation of plant reproduction according to NCERT science concepts.
