What is the correct ploidy sequence in the following ?
(A) Protonema cell of moss
(B) ovum of liverworts
(C) Roots cell of Pteridophyta
(D) Gymnospermic endosperm

Options

A. n, n, 2n, n
B. n, 2n, 2n, n
C. n, n, 2n, 3n
D. n, 2n, 2n, 3n

Answer

To determine the correct ploidy sequence for the given structures, we need to analyze each one based on their developmental origins and the type of plant they belong to.

### Step-by-Step Solution:

1. **Protonema cell of moss (A)**:
- The protonema in moss develops from haploid spores. Since spores are haploid (N), the protonema, which arises from these spores, is also haploid.
- **Ploidy**: N (Haploid)

2. **Ovum of liverworts (B)**:
- In liverworts, which are bryophytes, the main plant body is a gametophyte. The female gametophyte produces eggs (ovum) through mitosis. Since gametes (including ovum) are always haploid, the ovum of liverworts is also haploid.
- **Ploidy**: N (Haploid)

3. **Roots cell of Pteridophyta (C)**:
- Pteridophytes (like ferns) have a dominant sporophyte generation. The root cells of these plants are part of the sporophyte, which is diploid. Therefore, the root cells of Pteridophyta are diploid.
- **Ploidy**: 2N (Diploid)

4. **Gymnospermic endosperm (D)**:
- In gymnosperms, the endosperm is formed from the fertilization of the egg cell and is typically haploid, as it develops from the female gametophyte tissue. Therefore, the gymnospermic endosperm is also haploid.
- **Ploidy**: N (Haploid)

### Summary of Ploidy:
- (A) Protonema cell of moss: N
- (B) Ovum of liverworts: N
- (C) Roots cell of Pteridophyta: 2N
- (D) Gymnospermic endosperm: N

### Correct Ploidy Sequence:
The correct ploidy sequence is:
- (A) N
- (B) N
- (C) 2N
- (D) N

### Final Answer:
The correct ploidy sequence is: **N, N, 2N, N**.

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