The term 'self sterility' implies

Options

A. when pollen grains are sterile
B. when pollen grains do not germinate
C. when ovules are not fertile
D. when flowers are neuter

Answer

**Step-by-Step Solution:**

1. **Understanding Self Sterility**: The term 'self sterility' refers to a condition in flowering plants where an individual plant cannot fertilize its own ovules with its own pollen. This means that self-fertilization does not occur.

2. **Identifying the Context**: Self sterility is commonly found in hermaphrodite organisms, which possess both male and female reproductive structures. Despite having both structures, these plants cannot achieve fertilization through their own pollen.

3. **Mechanism of Self Sterility**: In self-sterile plants, the pollen grains produced by the plant do not germinate on the stigma of the same flower or another flower of the same plant. This prevents the formation of a zygote, which is necessary for seed development.

4. **Evaluating the Options**:
- Option A: When pollen grains are sterile - This does not accurately describe self sterility.
- Option B: When pollen grains do not germinate - This is the correct definition as it directly relates to the inability of self-fertilization.
- Option C: When ovules are not fertile - This is not a correct interpretation of self sterility.
- Option D: When flowers are neutered - This does not pertain to the concept of self sterility.

5. **Conclusion**: Based on the definitions and explanations, the correct answer to the question is Option B: when pollen grains do not germinate.

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