There are essentially two main types of self-fertilization (also known as self-pollination) in plants: autogamy and geitonogamy.
Types of Self-Fertilization
Here's a breakdown of each type:
Autogamy
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Definition: Autogamy is the process where pollen is transferred from the anther to the stigma of the same flower. Essentially, a flower fertilizes itself.
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Mechanism: This requires the flower to be bisexual (having both male and female reproductive parts). Often, flowers exhibiting autogamy don't even open (cleistogamy), ensuring self-pollination. In other cases, the anthers and stigma mature at the same time and are positioned close enough that pollen transfer is highly likely.
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Example: Some varieties of peas, wheat, and barley. Viola odorata (common violet) exhibits cleistogamy.
Geitonogamy
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Definition: Geitonogamy involves the transfer of pollen from the anther of one flower to the stigma of another flower on the same plant.
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Mechanism: While it involves cross-pollination within the same plant, it's still considered a type of self-fertilization because the genes involved are essentially the same. The plant is essentially cloning itself through seed. This occurs in monoecious plants (plants that have separate male and female flowers on the same individual).
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Example: Corn (maize) is a good example. Other examples include cucumbers, melons, and pumpkins.
Summary Table
| Type | Pollen Transfer | Genetic Diversity | Flowers Involved |
|---|---|---|---|
| Autogamy | Anther to stigma of the same flower | Very Low | Single bisexual flower |
| Geitonogamy | Anther of one flower to stigma of another on the same plant | Low | Multiple flowers on the same plant |
In conclusion, while both autogamy and geitonogamy result in self-fertilization, they differ in the specific floral structures involved in pollen transfer. Autogamy involves fertilization within a single flower, whereas geitonogamy occurs between different flowers on the same plant.
