Occurrence of triploid primary endosperm nucleus is cheracteristic of

Options

A. Algae
B. Bryophyte
C. Gymnosperms
D. Angiosperms.

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Question**: The question asks about the occurrence of a triploid primary endosperm nucleus and which group of plants it is characteristic of. The options provided are algae, bryophytes, gymnosperms, and angiosperms.

2. **Identifying Key Concepts**:
- The term "triploid" refers to a cell or organism that has three sets of chromosomes.
- The "primary endosperm nucleus" is formed during the fertilization process in plants.

3. **Explaining Double Fertilization**:
- In angiosperms (flowering plants), a unique process called double fertilization occurs. This involves two male gametes from the pollen grain.
- One male gamete fuses with the egg cell to form a diploid zygote, which develops into the embryo.

4. **Formation of the Primary Endosperm Nucleus**:
- The second male gamete fuses with the secondary nucleus (which is formed by the fusion of two polar nuclei) to produce the primary endosperm nucleus.
- Since the secondary nucleus is diploid (two sets of chromosomes), the fusion with the haploid male gamete results in a triploid structure (three sets of chromosomes).

5. **Conclusion**:
- The primary endosperm nucleus, which is triploid, later develops into the endosperm, providing nourishment to the developing embryo.
- This process of double fertilization and the formation of a triploid primary endosperm nucleus is a characteristic feature of angiosperms.

6. **Final Answer**: Therefore, the occurrence of a triploid primary endosperm nucleus is characteristic of **angiosperms**.

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