Module: | Double Fertilization & Endosperm
Q77: Consider the following statements regarding the structural polarity of the synergid and its role in tube arrest:
1. A mature synergid cell exhibits intense structural polarity, uniquely possessing a large chalazal vacuole and a micropylar nucleus.
2. Guided by the filiform apparatus, the entering pollen tube typically bursts and discharges its gametic contents directly into this large synergid vacuole.
3. The highly acidic pH of the synergid vacuole acts as an instant defense mechanism, physically dissolving the male gametes to prevent polyspermy.
Which of the above statements is/are correct?
2. Guided by the filiform apparatus, the entering pollen tube typically bursts and discharges its gametic contents directly into this large synergid vacuole.
3. The highly acidic pH of the synergid vacuole acts as an instant defense mechanism, physically dissolving the male gametes to prevent polyspermy.
Which of the above statements is/are correct?
✅ Correct Answer: A
The correct option is A. Statements 1 and 2 are correct, whereas Statement 3 is incorrect.
The synergids flanking the egg cell are highly specialized.
Structurally, they exhibit a specific polarity: the nucleus is located near the micropylar end (close to the filiform apparatus), while a massive vacuole occupies the chalazal end of the cell.
When the pollen tube enters through the micropyle, it penetrates the degenerating synergid.
The osmotic pressure differentials cause the tube tip to burst, violently expelling the two male gametes and the vegetative nucleus directly into the large chalazal vacuole of the synergid.
Statement 3 presents a fictional physiological mechanism.
The vacuole does not dissolve the gametes; if it did, fertilization would fail entirely.
Instead, the gametes survive the discharge and utilize actin coronas to actively migrate out of the synergid and toward their respective targets (the egg and the central cell).
The synergids flanking the egg cell are highly specialized.
Structurally, they exhibit a specific polarity: the nucleus is located near the micropylar end (close to the filiform apparatus), while a massive vacuole occupies the chalazal end of the cell.
When the pollen tube enters through the micropyle, it penetrates the degenerating synergid.
The osmotic pressure differentials cause the tube tip to burst, violently expelling the two male gametes and the vegetative nucleus directly into the large chalazal vacuole of the synergid.
Statement 3 presents a fictional physiological mechanism.
The vacuole does not dissolve the gametes; if it did, fertilization would fail entirely.
Instead, the gametes survive the discharge and utilize actin coronas to actively migrate out of the synergid and toward their respective targets (the egg and the central cell).