Which are the nuclei that fuse to form endosperm?

Answer

To answer the question, "Which are the nuclei that fuse to form endosperm?" we will follow these steps:

### Step-by-Step Solution:

1. **Understanding the Structure of the Embryo Sac**:
- The embryo sac, or female gametophyte, is a crucial structure in flowering plants (angiosperms). It contains several types of cells including antipodal cells, synergids, an egg cell, and polar nuclei.

2. **Identifying the Key Components**:
- At the chalazal end of the embryo sac, there are three antipodal cells.
- At the micropylar end, there are two synergids and one egg cell.
- The central part of the embryo sac contains two polar nuclei.

3. **Pollen Tube and Male Gametes**:
- When fertilization occurs, a pollen tube penetrates the embryo sac from the micropylar end, carrying two male gametes.

4. **Fusion Events**:
- One of the male gametes fuses with the egg cell to form a diploid zygote.
- The second male gamete fuses with the two polar nuclei present in the central cell of the embryo sac.

5. **Formation of Endosperm**:
- The fusion of the second male gamete with the two polar nuclei results in the formation of the endosperm, which is a triploid tissue (3n). This triploid nature arises because it consists of one set of chromosomes from the male gamete and two sets from the polar nuclei.

6. **Conclusion**:
- Therefore, the nuclei that fuse to form the endosperm are **one male gamete and two polar nuclei**.

### Summary:
The endosperm is formed by the fusion of **one male gamete** with **two polar nuclei** in the embryo sac of flowering plants.

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