What is self-incompatibility ?

Explanation

**Step-by-Step Solution:**

1. **Definition of Self-Incompatibility**: Self-incompatibility is a genetic mechanism found in some flowering plants that prevents self-pollination. It ensures that pollen from the same plant does not fertilize its ovules.

2. **Purpose of Self-Incompatibility**: The primary purpose of self-incompatibility is to promote genetic diversity by encouraging cross-pollination. This is crucial for the survival and adaptation of plant species.

3. **Mechanism of Self-Incompatibility**: In self-incompatible plants, even if the pollen grains are viable (capable of fertilization), they are prevented from germinating on the stigma of the same flower. This is a genetically controlled process that ensures that the pollen from the same plant does not fertilize its own ovules.

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