1. Define pollination and explain its significance in angiosperms.
Answer:
Pollination is the process of transferring pollen grains from the male anther of a flower to the female stigma. It is a crucial step in sexual reproduction for angiosperms, facilitating fertilization and the production of seeds.
Significance:
- Ensures genetic diversity.
- Facilitates plant reproduction.
- Promotes fruit and seed formation.
- Maintains ecological balance by involving pollinators.
2. What are the types of pollination? Describe each briefly.
Answer:
Pollination can be classified into:
- Self-pollination: Transfer of pollen within the same flower (autogamy) or between flowers of the same plant (geitonogamy).
- Ensures purity of the species.
- Limited genetic diversity.
- Cross-pollination: Transfer of pollen between flowers of different plants of the same species.
- Promotes genetic variation.
- Depends on external agents like wind, water, or animals.
3. Describe the adaptations of flowers for self-pollination.
Answer:
Flowers adapted for self-pollination exhibit:
- Cleistogamy: Flowers do not open, ensuring self-pollination (e.g., Viola).
- Homogamy: Simultaneous maturation of anther and stigma.
- Proximity of Anther and Stigma: Enhances chances of pollen transfer within the same flower.
4. Explain the role of external agents in cross-pollination.
Answer:
Cross-pollination depends on agents like:
- Wind (Anemophily):
- Lightweight, non-sticky pollen.
- Feathery stigmas to trap pollen.
- Water (Hydrophily):
- Common in aquatic plants like Vallisneria.
- Pollen floats and reaches the stigma.
- Insects (Entomophily):
- Bright, fragrant flowers attract insects.
- Nectar serves as a reward.
- Birds (Ornithophily):
- Large, colorful flowers with ample nectar attract birds.
- Bats (Chiropterophily):
- Large, nocturnal flowers attract bats.
5. What is the difference between autogamy and geitonogamy?
Answer:
| Feature | Autogamy | Geitonogamy |
|---|---|---|
| Definition | Pollen transfer within the same flower. | Pollen transfer between flowers of the same plant. |
| Genetic Impact | No genetic variation. | Limited genetic variation. |
| Dependency | Independent of pollinators. | May involve pollinators. |
6. Discuss the structure of wind-pollinated flowers and their adaptations.
Answer:
Structure and Adaptations:
- Small, inconspicuous flowers.
- Absence of scent and nectar.
- Lightweight, smooth pollen for easy dispersal.
- Feathery stigmas to capture pollen.
Example: Maize and grasses.
7. What are the characteristics of insect-pollinated flowers?
Answer:
- Brightly colored petals.
- Fragrant or scented flowers.
- Presence of nectar as a reward.
- Sticky or spiny pollen for adhesion.
- Landing platforms for pollinators.
Examples: Sunflower, Rose, Marigold.
8. How do hydrophilous plants adapt for water pollination?
Answer:
- Pollen grains are water-resistant.
- Long, ribbon-like stigmas.
- Male and female flowers are submerged or floating.
- Pollen is released into the water to drift towards the stigma.
Examples: Vallisneria, Hydrilla.
9. Explain chiropterophily with examples.
Answer:
Chiropterophily refers to pollination by bats.
Adaptations:
- Nocturnal flowers with large sizes.
- Strong, musty odor to attract bats.
- Ample nectar supply.
- Sturdy structures to withstand bat visits.
Examples: Baobab, Agave.
10. What is ornithophily? Describe its floral adaptations.
Answer:
Ornithophily is pollination by birds.
Adaptations:
- Bright red, orange, or yellow flowers.
- Tubular shape to accommodate bird beaks.
- Ample nectar production.
- No strong scent as birds rely on vision.
Examples: Hibiscus, Bottlebrush.
11. Describe the process of pollination in Vallisneria.
Answer:
- Male flowers detach and float on the water surface.
- Female flowers have long stalks that reach the surface.
- Pollen grains float to the stigma of the female flowers.
This ensures successful pollination in aquatic environments.
12. What is the significance of pollination syndromes?
Answer:
Pollination syndromes are sets of traits in flowers that attract specific pollinators.
Importance:
- Ensures efficient pollen transfer.
- Enhances plant-pollinator interactions.
- Maintains biodiversity and ecological stability.
13. Differentiate between biotic and abiotic pollination.
Answer:
| Feature | Biotic Pollination | Abiotic Pollination |
|---|---|---|
| Definition | Involves living agents like insects, birds, or bats. | Involves non-living agents like wind or water. |
| Examples | Entomophily, Ornithophily, Chiropterophily. | Anemophily, Hydrophily. |
14. What is the ecological importance of pollination?
Answer:
- Maintains genetic diversity.
- Supports ecosystem services like food production.
- Promotes co-evolution between plants and pollinators.
- Ensures survival of many plant species.
15. Describe the role of nectar guides in pollination.
Answer:
Nectar guides are patterns on petals visible to pollinators.
Role:
- Direct pollinators to nectar and reproductive structures.
- Enhance efficiency of pollen transfer.
- Common in insect-pollinated flowers like orchids.
16. What is the role of co-evolution in pollination?
Answer:
Co-evolution is the mutual adaptation between plants and pollinators.
Examples:
- Long-tubed flowers and long-tongued moths.
- Specialized pollination in figs by fig wasps.
17. What are the limitations of self-pollination?
Answer:
- Limited genetic diversity.
- Reduced adaptability to environmental changes.
- Accumulation of deleterious mutations.
18. How do flowers prevent self-pollination?
Answer:
- Dichogamy: Different maturation times of anther and stigma.
- Herkogamy: Physical separation of reproductive organs.
- Self-incompatibility: Genetic mechanisms prevent self-pollen germination.
19. Explain geitonogamy and its significance.
Answer:
Geitonogamy involves pollen transfer between flowers on the same plant.
- Technically self-pollination.
- Offers limited genetic variation compared to cross-pollination.
20. What are the advantages and disadvantages of cross-pollination?
Answer:
Advantages:
- Genetic diversity.
- Improved adaptability.
- Enhanced survival of species.
Disadvantages:
- Dependent on external agents.
- Requires more energy for floral adaptations.
These descriptive questions and answers provide a comprehensive understanding of pollination mechanisms in angiosperms.
