- A A simple physical size restriction at the narrow micropyle opening that permits only one pollen tube through at a time
- B Synergid cells sending signals to block subsequent pollen tube entry after the first tube enters and bursts
- C The developing endosperm tissue actively repelling any additional pollen tubes immediately after fertilization occurs
- D Specialized anti-pollen enzymes that are secreted directly by the egg cell cytoplasm itself before fertilization
Correct answer: B. Synergid cells sending signals to block subsequent pollen tube entry after the first tube enters and bursts
Explanation: After first pollen tube enters synergid and bursts, the unfused synergid sends a rapid signal preventing other pollen tubes from entering. Mechanism involves changes in synergid and central cell signaling.
Concept context
Flower structure, pollination, double fertilization, and seed/fruit development — the highest-scoring Class 12 biology chapter in NEET.
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