A dioecious flowering plant prevents both

Options

A. autogamy and xenogamy
B. autogamy and geitonogamy
C. geitonogamy and xenogamy
D. cleistogamy and xenogamy

Answer

To answer the question regarding what a dioecious flowering plant prevents, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definitions**:
- **Dioecious Plants**: These are flowering plants that have male and female flowers on separate plants. This means that one plant will produce only male flowers, while another will produce only female flowers.
- **Monoecious Plants**: In contrast, these plants have both male and female flowers on the same individual.

2. **Identify Pollination Types**:
- **Autogamy**: This is a form of self-pollination where the pollen from the same flower fertilizes its ovules.
- **Xenogamy**: This refers to cross-pollination where pollen from one plant fertilizes the ovules of another plant.
- **Zitonogamy**: This is a type of self-pollination where different flowers on the same plant are involved.
- **Clistogamy**: This involves non-opening flowers that self-pollinate, typically in unfavorable conditions.

3. **Determine What Dioecious Plants Prevent**:
- Since dioecious plants have male and female flowers on separate plants, they cannot undergo autogamy (self-pollination) because there are no male and female parts on the same plant.
- They also prevent zitonogamy because this type of self-pollination involves different flowers on the same plant, which is not applicable to dioecious plants.

4. **Conclusion**:
- Therefore, dioecious flowering plants prevent both autogamy and zitonogamy.

5. **Select the Correct Option**:
- Based on the analysis, the correct answer is **autogamy and zitonogamy**.

### Final Answer:
A dioecious flowering plant prevents both **autogamy and zitonogamy**.

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