Question

Mention the ploidy of the following: protonemal cell of a moss; primary endosperm nucleus in dicot, leaf cell of a moss; prothallus cell of a ferm; gemma cell in Marchantia; meristem cell of monocot, ovum of a liverwort, and zygote of a fern.

Answer 1

 

• Protonemal cell of a moss
• Primary endosperm nucleus in dicot
• Leaf cell of a moss
• Prothallus cell of a fern
• Gemma cell in Marchantia
• Meristem cell of a monocot
• Ovum of a liverwort
• Zygote of a fern

Key Idea: Ploidy

Ploidy refers to the number of sets of chromosomes present in a cell. A haploid cell has one set of chromosomes and is denoted by n, while a diploid cell has two sets of chromosomes and is denoted by 2n. Triploid cells have three sets and are denoted by 3n.

Answers with Explanation

• Protonemal cell of a moss: This is part of the gametophyte (dominant haploid) generation in moss. Hence it is haploid .
• Primary endosperm nucleus in dicot: Formed by fusion of one male gamete n with two polar nuclei \((n + n)\) during double fertilization, so total is n + n + n = 3n. Hence it is triploid .
• Leaf cell of a moss: The leafy plant body of moss is a gametophyte, so its somatic cells are haploid .
• Prothallus cell of a fern: The prothallus is the independent gametophyte in ferns, so its cells are haploid .
• Gemma cell in Marchantia: Gemmae are asexual reproductive bodies produced by the gametophyte and give rise to new gametophytes. Therefore gemma cells are haploid .
• Meristem cell of a monocot: The main plant body of flowering plants (including monocots) is a sporophyte and is diploid, so its meristematic cells are diploid .
• Ovum of a liverwort: The ovum is a female gamete produced by the gametophyte and therefore is a haploid  cell.
• Zygote of a fern: The zygote is formed by fusion of male and female gametes, n + n = 2n, so it is diploid .

Final Summary (Compact Form)

• Protonemal cell of a moss – n (haploid)
• Primary endosperm nucleus in dicot – 3n (triploid)
• Leaf cell of a moss – n (haploid)
• Prothallus cell of a fern – n (haploid)
• Gemma cell in Marchantia – n (haploid)
• Meristem cell of a monocot – 2n (diploid)
• Ovum of a liverwort – n (haploid)
• Zygote of a fern – 2n (diploid)