Pollination is the process of transfer of pollen grains from the anther (male part of flower) to the stigma (female part of flower). It is an important step for fertilization and seed formation in flowering plants.
Pollination is mainly of two types:
- Self-pollination
- Cross-pollination
1. Self-Pollination
Self-pollination is the transfer of pollen grains from the anther to the stigma of the same flower or another flower of the same plant.
It helps plants to produce seeds without depending much on external agents like wind, water, or insects.
Types of Self-Pollination
i) Autogamy
Autogamy is the transfer of pollen grains from the anther to the stigma of the same flower.
This usually occurs in bisexual flowers where both male and female reproductive organs are present together.
Features of Autogamy
- Occurs within the same flower
- Flowers are generally bisexual
- Less wastage of pollen grains
- Maintains purity of characters
Autogamy is again of two types:
a) Chasmogamous Flowers
Chasmogamous flowers are flowers that open fully and expose their anthers and stigma.
Pollination may occur naturally inside the flower.
Examples-
Oxalis, Hibiscus, Mustard, Pea
Characteristics
- Flowers are open
- Anthers and stigma are visible
- May allow both self and cross-pollination
b) Cleistogamous Flowers
Cleistogamous flowers are flowers that do not open at all. Pollination occurs inside the closed flower.
These flowers always perform self-pollination.
Examples
Characteristics
- Flowers remain closed
- Assured seed formation
- No need of pollinating agents
- Very little wastage of pollen grains
Advantages of Self-Pollination
- Maintains pure genetic characters
- Requires less pollen
- Assured fertilization
- Useful when pollinating agents are absent
Disadvantages of Self-Pollination
- Produces less genetic variation
- New characters are rarely formed
- Plants may become weak after many generations
2. Cross-Pollination
Cross-pollination is the transfer of pollen grains from the anther of one flower to the stigma of another flower.
It usually occurs between flowers of different plants of the same species.
Cross-pollination increases genetic variation and produces healthier plants.
Types of Cross-Pollination
a) Geitonogamy
Geitonogamy is the transfer of pollen grains from the anther of one flower to the stigma of another flower of the same plant.
Although pollen moves between two flowers, both flowers belong to the same plant.
Examples
Characteristics
- Involves two flowers of the same plant
- Genetically similar to self-pollination
- Often requires agents like wind or insects
b) Xenogamy
Xenogamy is the transfer of pollen grains from the anther of one plant to the stigma of a flower on a different plant of the same species.
It is the true form of cross-pollination.
Examples
Characteristics
- Occurs between different plants
- Produces genetic variation
- Depends on pollinating agents like insects, wind, water, birds, etc.
Advantages of Cross-Pollination
- Produces healthy and strong plants
- Increases genetic variation
- Helps in evolution and adaptation
- Reduces harmful genetic defects
Disadvantages of Cross-Pollination
- Large amount of pollen grains are wasted
- Depends on external pollinating agents
- Pollination may fail in absence of agents
Agents of Pollination
Different agents help in pollination:
- Wind – Maize, grasses
- Water – Vallisneria
- Insects – Sunflower, Hibiscus
- Birds – Erythrina
- Bats – Kigelia
Summary Table
| Type | Definition | Example |
|---|---|---|
| Autogamy | Pollen transfer within same flower | Oxalis, Pea |
| Chasmogamy | Open flowers | Hibiscus, Mustard |
| Cleistogamy | Closed flowers | Commelina, Viola |
| Geitonogamy | Between flowers of same plant | Maize, Coconut |
| Xenogamy | Between flowers of different plants | Sunflower, Papaya |
Pollination is essential for reproduction in flowering plants. Self-pollination ensures certainty of seed formation, while cross-pollination increases variation and produces healthier offspring. Both types play an important role in maintaining plant life and biodiversity.
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