In angiosperm, syngamy or true fertilization refers to

Options

A. fusion of a sperm with secondary nucleus of form zygote
B. fusion of sperm with oosphere
C. fusion of one sperm with egg and other with secondary nucleus
D. fusion of one of the sperm with a synergid

Answer

**Step-by-Step Solution:**

1. **Understanding Angiosperms**: Angiosperms are flowering plants characterized by seeds that are enclosed within fruits. This is the basic definition that sets the context for the question.

2. **Structure of the Ovule**: Within the ovary of angiosperms, there are structures called ovules. Each ovule contains several types of cells, including:
- Three antipodal cells
- One egg cell (also referred to as the oospere)
- Two synergids
- One secondary nucleus (which is made up of two polar nuclei)

3. **Defining Syngamy**: Syngamy refers to the fusion of two gametes. In the context of angiosperms, this specifically means the fusion of a sperm cell with an egg cell (oospere) to form a zygote. This process is considered true fertilization.

4. **Analyzing the Options**:
- **Option 1**: Fusion of sperm with a secondary nucleus to form a zygote. This is incorrect because the secondary nucleus fuses with another sperm to form the endosperm, not the zygote.
- **Option 2**: Fusion of sperm with oospere (egg cell) to form a zygote. This is correct and represents true fertilization (syngamy).
- **Option 3**: Fusion of one sperm with the egg and another sperm with the secondary nucleus. This describes double fertilization, which occurs in angiosperms but is not the definition of syngamy.
- **Option 4**: Fusion of one sperm with a synergid. This is incorrect as synergids do not participate in the formation of the zygote and lead to polyembryony.

5. **Conclusion**: The correct answer is **Option 2**: the fusion of sperm with oospere to form a zygote is referred to as true fertilization or syngamy.

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