In angiosperms, normally after fertilisation

Options

A. the zygote divides earlier than the primary endosperm nucleus
B. the primary endosperm nucleus divides earlier than the zygote
C. both the zygote and primary endosperm nuclei divide simultaneously
D. both the zygote and primary endosperm nuclei undergo a resting period.

Answer

**Step-by-Step Solution:**

1. **Understanding Fertilization in Angiosperms**: In angiosperms, fertilization occurs when the male gamete (sperm) fuses with the female gamete (egg cell) to form a zygote. Additionally, another sperm fuses with two polar nuclei to form the primary endosperm nucleus (PEN).

2. **Identifying the Products of Fertilization**: After fertilization, two key structures are formed:
- The zygote, which will develop into the embryo.
- The primary endosperm nucleus (PEN), which will develop into the endosperm that nourishes the embryo.

3. **Sequence of Division**: The question asks about the sequence of division between the zygote and the primary endosperm nucleus:
- The primary endosperm nucleus typically divides before the zygote. This is because the endosperm needs to be established first to provide nourishment for the developing embryo.

4. **Evaluating the Options**:
- **Option A**: "The zygote divides earlier than the primary endosperm nucleus" - This is incorrect.
- **Option B**: "The primary endosperm nucleus divides earlier than the zygote" - This is correct.
- **Option C**: "Both the zygote and primary endosperm nuclei divide simultaneously" - This is incorrect.
- **Option D**: "Both the zygote and primary endosperm nuclei undergo a resting period" - This is incorrect.

5. **Conclusion**: Based on the sequence of events after fertilization in angiosperms, the correct answer is that the primary endosperm nucleus divides earlier than the zygote.

**Final Answer**: The correct option is B: "The primary endosperm nucleus divides earlier than the zygote."

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