In over 60% of angiosperms pollen grains are shed at

Options

A. One celled stage
B. Three nuclei stage
C. Two celled stage
D. Three celled stage

Answer

**Step-by-Step Solution:**

1. **Understanding Pollen Grain Development**: Pollen grains develop from a diploid cell known as the microspore mother cell or pollen mother cell. This cell undergoes meiosis, resulting in the formation of four haploid pollen grains.

2. **Formation of Pollen Tetrad**: The four pollen grains produced from the microspore mother cell are collectively referred to as a pollen tetrad. Each of these grains is haploid and will eventually be released.

3. **Cell Division in Pollen Grains**: Each haploid pollen grain undergoes mitosis. This process results in the formation of two types of cells within the pollen grain: a larger vegetative cell and a smaller generative cell. This stage is referred to as the two-cell stage.

4. **Further Division of Generative Cell**: The generative cell can further divide by mitosis to produce two male gametes. At this point, the pollen grain is referred to as being in the three-cell stage, which includes one vegetative cell and two male gametes.

5. **Pollen Grain Shedding in Angiosperms**: In over 60% of angiosperms, pollen grains are shed at the two-cell stage, which consists of one vegetative cell and one generative cell. In contrast, about 40% of angiosperms shed pollen grains at the three-cell stage.

6. **Conclusion**: Therefore, the correct answer to the question is that in over 60% of angiosperms, pollen grains are shed at the two-cell stage.

**Final Answer**: In over 60% of angiosperms, pollen grains are shed at the two-cell stage.

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