What is the chromosome number in calyptra, perichaetial cells, columella and protonema if endothecium cell contains 20 chromosomes?

Options

A. 10, 10, 20, and 10, respectively
B. 10, 20, 20, and 10, respectively
C. 20, 10, 20, and 10, respectively
D. 10, 10, 20, and 10, respectively

Answer

To determine the chromosome number in the calyptra, perichaetial cells, columella, and protonema when the endothecium cell contains 20 chromosomes, we need to understand the life cycle of mosses, particularly the role of meiosis and the types of cells involved.

### Step-by-Step Solution:

1. **Identify the Chromosome Number in Endothecium**:
- The endothecium cell is a spore mother cell (2n) that contains 20 chromosomes. This means it is diploid (2n = 20).

2. **Determine the Chromosome Number After Meiosis**:
- During meiosis, the endothecium undergoes division to produce spores. Each spore will have half the number of chromosomes, which means:
- Spores (n) = 20 / 2 = 10 chromosomes.

3. **Chromosome Number in Calyptra**:
- The calyptra forms after the meiosis and is derived from the spores. Since the calyptra is associated with the gametophyte generation, it will also have a haploid chromosome number:
- Calyptra (n) = 10 chromosomes.

4. **Chromosome Number in Perichaetial Cells**:
- Perichaetial cells are part of the gametophyte structure, similar to the calyptra. Therefore, they will also have a haploid chromosome number:
- Perichaetial cells (n) = 10 chromosomes.

5. **Chromosome Number in Columella**:
- The columella arises from the endothecium and is part of the sporophyte generation. Since it is derived from the diploid endothecium, it retains the diploid chromosome number:
- Columella (2n) = 20 chromosomes.

6. **Chromosome Number in Protonema**:
- The protonema is a vegetative structure that develops from the spores and is part of the gametophyte generation. Therefore, it will also have a haploid chromosome number:
- Protonema (n) = 10 chromosomes.

### Summary of Chromosome Numbers:
- **Calyptra**: 10 chromosomes (n)
- **Perichaetial Cells**: 10 chromosomes (n)
- **Columella**: 20 chromosomes (2n)
- **Protonema**: 10 chromosomes (n)

### Final Answer:
- Calyptra: 10
- Perichaetial Cells: 10
- Columella: 20
- Protonema: 10