In which of the following condition, autogamy is prevented but not geitonogamy ?

Options

A. Self - incompatibility of pollen and stigma .
B. Non-synchronization of pollen and anther release .
C. Monoecious condition
D. Dioecious condition

Answer

To solve the question, "In which of the following conditions, autogamy is prevented but not geitonogamy?", we will analyze the definitions of autogamy and geitonogamy, and then evaluate the given options.

### Step-by-Step Solution:

1. **Understanding Autogamy and Geitonogamy**:
- **Autogamy**: This is a form of self-fertilization where pollen from the same flower fertilizes the ovule of that same flower.
- **Geitonogamy**: This is a type of cross-fertilization where pollen from one flower fertilizes the ovule of another flower on the same plant.

2. **Analyzing the Options**:
- **Option 1: Self incompatibility of the pollen and stigma**:
- Self-incompatibility prevents autogamy because the pollen cannot fertilize the ovule of the same flower. However, it does not prevent geitonogamy since pollen from another flower can still fertilize the ovule.
- **Conclusion**: This option does not fit the requirement.

- **Option 2: Non-synchronization of pollen and anther release**:
- If the pollen and anther are not synchronized, it means that the pollen is not available when the stigma is receptive. This would prevent both autogamy and geitonogamy.
- **Conclusion**: This option does not fit the requirement.

- **Option 3: Monoecious condition**:
- In a monoecious condition, both male and female reproductive organs are present on the same plant but in different flowers. Autogamy is prevented because the pollen from one flower cannot fertilize the ovule of another flower on the same plant. However, geitonogamy is possible since pollen from one flower can fertilize the ovule of another flower on the same plant.
- **Conclusion**: This option fits the requirement.

- **Option 4: Dioecious condition**:
- In a dioecious condition, male and female reproductive organs are on different plants. This condition prevents both autogamy and geitonogamy since fertilization cannot occur between different plants.
- **Conclusion**: This option does not fit the requirement.

3. **Final Answer**:
- The correct answer is **Option 3: Monoecious condition**.