Dichogamy in plants is the temporal separation of the maturation of the anthers and stigma within a flower to prevent self-pollination. In simpler terms, the male and female parts of the flower mature at different times. This is a clever mechanism plants use to encourage cross-pollination, promoting genetic diversity.
Types of Dichogamy
There are two primary types of dichogamy:
- Protandry: This occurs when the anthers, the male parts of the flower, mature and release pollen before the stigma, the female part, is receptive.
- Protogyny: This is the opposite of protandry, where the stigma becomes receptive before the anthers mature and release pollen.
| Dichogamy Type | Male Part (Anthers) | Female Part (Stigma) |
|---|---|---|
| Protandry | Matures First | Matures Second |
| Protogyny | Matures Second | Matures First |
Why Dichogamy?
The primary reason for dichogamy is to reduce or eliminate self-pollination, also known as autogamy. Self-pollination can lead to inbreeding depression, reducing the fitness and adaptability of plant populations. Dichogamy promotes outcrossing (cross-pollination), which increases genetic variation and enhances the plant's ability to adapt to changing environmental conditions.
Examples
While many plants employ dichogamy, here are a few examples:
- Protandry: Sunflowers (Helianthus annuus) are a classic example of protandry. The anthers mature and shed pollen before the stigma becomes receptive.
- Protogyny: Avocado (Persea americana) exhibits protogyny. The stigma is receptive before the pollen is released. Avocado trees even have different flowering types (A and B) that further ensure cross-pollination.
Dichogamy is therefore a crucial adaptation strategy for plants seeking to maximize genetic diversity through cross-pollination.
