PEN stands for

Options

A. Primary endosperm nourishment
B. Primary endosperm nucleus
C. Primary embryo nourishment
D. Poly embryo nourishment.

Answer

**Step-by-Step Solution:**

1. **Understanding the Acronym:** The question asks what PEN stands for in a biological context. The options provided are:
- Primary Endosperm Nourishment
- Primary Endosperm Nucleus
- Primary Embryo Nourishment
- Polyembryon Nourishment

2. **Identifying the Correct Option:** To determine the correct answer, we need to understand the biological process related to endosperm formation in flowering plants.

3. **Triple Fusion Process:** In flowering plants, during fertilization, a process called triple fusion occurs. This involves the fusion of one male gamete with the diploid secondary nucleus (formed by the fusion of two polar nuclei).

4. **Formation of Primary Endosperm Nucleus:** The fusion of the haploid male gamete with the diploid secondary nucleus results in the formation of the primary endosperm nucleus (PEN). This structure is triploid (3n) because it contains three sets of chromosomes: two from the polar nuclei and one from the male gamete.

5. **Conclusion:** Based on the process described, the correct answer to the question "PEN stands for" is **Primary Endosperm Nucleus**.

**Final Answer:** PEN stands for **Primary Endosperm Nucleus**.

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