What does self incompatibility provides for a plant ?

Options

A. Means of transferring pollen to another plant
B. Means of coordinating the fertilization of egg with the development of store before if fertilize the egg cell
C. A mean of destroying foreign pollen before it fertilizes the egg cell
D. A biological block to self fertilization so that cross fertilization is assured

Answer

### Step-by-Step Solution:

1. **Understanding Self-Incompatibility**: Self-incompatibility is a genetic mechanism in flowering plants that prevents self-fertilization. This means that a plant cannot fertilize its own ovules with its own pollen.

2. **Mechanism of Self-Incompatibility**: The mechanism works by inhibiting the germination of pollen or the growth of the pollen tube in the pistil. This inhibition occurs due to interactions between specific chemicals present in the pollen and the stigma (the receptive part of the pistil).

3. **Purpose of Self-Incompatibility**: The primary purpose of self-incompatibility is to promote genetic diversity by ensuring that cross-fertilization occurs rather than self-fertilization. This is important for the health and adaptability of plant populations.

4. **Biological Block**: Self-incompatibility acts as a biological block to self-fertilization, which means it prevents the plant from using its own pollen to fertilize its ovules. This mechanism ensures that the plant must rely on pollen from other individuals for fertilization.

5. **Conclusion**: Therefore, self-incompatibility provides a biological block to self-fertilization, ensuring that cross-fertilization is assured, which enhances genetic diversity within the plant population.

### Final Answer:
Self-incompatibility provides a biological block to self-fertilization so that cross-fertilization is assured.

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