Herkogamy in botany refers to the spatial separation of the anthers and stigmas within a flower. This separation is a key floral trait that promotes outcrossing, or the avoidance of interference between male and female sexual functions (Webb and Lloyd 1986). In simpler terms, it's a physical arrangement inside a flower that helps prevent self-pollination.
Understanding Herkogamy
Herkogamy is a strategy flowers use to reduce self-pollination and encourage cross-pollination. This increases genetic diversity among plants.
Here's a breakdown:
- Anthers: The part of the flower that produces pollen.
- Stigmas: The part of the flower that receives pollen.
- Spatial Separation: The physical distance or arrangement that keeps anthers and stigmas apart.
- Outcrossing: Cross-pollination, or pollination between different plants.
Why is Herkogamy Important?
- Promotes Genetic Diversity: By encouraging outcrossing, herkogamy helps create genetic variation within plant populations.
- Reduces Inbreeding Depression: Self-pollination can lead to inbreeding depression, where offspring have reduced fitness. Herkogamy minimizes this risk.
- Avoidance of Interference: Herkogamy ensures there is no physical interference between the plants own male and female sexual function, thus promoting maximum use of resources.
Types of Herkogamy
While the basic principle remains the same, the specific way anthers and stigmas are separated can vary:
| Type | Description |
|---|---|
| Approach | The stigma is positioned above the anthers, so pollinators contact the stigma first when approaching the flower. |
| Reverse | The anthers are positioned above the stigma, forcing the pollinator to contact them first. |
| Flexistyly | The style (supporting the stigma) bends away from the anthers during pollen shed and then returns to its original position when receptive. |
| Enantiostyly | The style (supporting the stigma) is deflected to either the left or right of the flowers centre. |
| Heterostyly | Flowers exist in different morphs in the plant population. Different morphs show reciprocal arrangement of styles and stamens. |
Examples of Herkogamy
Many plant species exhibit herkogamy, each with unique adaptations. Some examples include:
- Irises: Often have stigmas that are positioned above the anthers.
- Primroses: Exhibit heterostyly, with different flower forms having different anther and stigma positions.
