Understanding Cell Ploidy Levels

Ploidy refers to the number of complete sets of chromosomes within a biological cell. Key terms include:

• Haploid (n): Contains one set of chromosomes (e.g., gametes).
• Diploid (2n): Contains two sets of chromosomes (e.g., zygote, somatic cells).
• Triploid (3n): Contains three sets of chromosomes.

Analyzing Options in Angiosperm Reproduction

Let's examine the ploidy of each option during double fertilization in angiosperms:

• Zygote: Formed by the fusion of a male gamete (n) and the egg cell (n). Therefore, the zygote is diploid, represented as $n + n = 2n$.
• Central cell: Before fertilization, the central cell contains two polar nuclei, making it effectively diploid ($n + n = 2n$).
• Primary endosperm cell: This cell results from the fusion of a male gamete (n) with the central cell's polar nuclei ($2n$). This fusion, known as triple fusion, results in a triploid nucleus: $n + 2n = 3n$. This cell develops into the endosperm, which nourishes the embryo.
• Synergid: These are haploid cells (n) located within the ovule, near the egg cell.

Identifying the Triploid Cell

Based on the analysis:

• The primary endosperm cell is formed through triple fusion ($n + 2n$) and is therefore triploid ($3n$).

Thus, the primary endosperm cell is the triploid cell among the choices.