Monosporic eight nucleate embryosac is in:

Question

Accepted Answer

The correct option is 4: Polygonum

The term "monosporic eight nucleate embryo sac" refers to the Polygonum-type of embryo sac development, which is the most common pattern found in approximately 70% of all flowering plant species. The development is classified as *monosporic* because the embryo sac originates from only one out of the four megaspores produced after the meiotic division of the diploid Megaspore Mother Cell (MMC). Following meiosis, a linear tetrad of four haploid megaspores is formed; the three micropylar megaspores typically degenerate, and the single remaining chalazal megaspore is the functional one. This functional megaspore then undergoes three successive free nuclear mitotic divisions, resulting in a total of eight haploid nuclei. These eight nuclei then organize to form the characteristic seven-celled structure: the egg apparatus (one egg cell and two synergids), the large central cell (containing two polar nuclei), and three antipodal cells at the chalazal end. Therefore, *Polygonum* is the classical and defining example of this specific mode of female gametophyte development.

The incorrect option is 1: Allium

The embryo sac development in *Allium* is classified as a *bisporic* type. This categorization is based on the fact that, after the Megaspore Mother Cell undergoes meiosis, only the first meiotic division is immediately followed by a cell wall formation, creating two cells. The nucleus in the micropylar cell degenerates, but the entire chalazal cell, which contains two haploid nuclei that are the product of meiosis I and II, remains functional. These two nuclei, along with the subsequent products of mitotic divisions, contribute to the formation of the embryo sac, thus involving the material of two original megaspores, which is the definition of bisporic development, not monosporic.

The incorrect option is 2: Frittilaria

The *Frittilaria* type of embryo sac development is classified as *tetrasporic*, meaning all four haploid nuclei derived from the Megaspore Mother Cell's meiosis participate in the embryo sac formation. This occurs because cell wall formation is suppressed after both meiotic divisions (Meiosis I and Meiosis II). The four haploid nuclei then arrange themselves in a unique configuration—one nucleus at the micropylar end and three at the chalazal end—before subsequent mitotic divisions. Since four megaspore nuclei contribute to the gametophyte structure, this process fundamentally differs from the monosporic development seen in *Polygonum*.

The incorrect option is 3: Plumbago

*Plumbago* also represents a *tetrasporic* mode of embryo sac development, where, like *Frittilaria*, all four meiotic products are functional due to the absence of cell wall formation during meiosis. However, the *Plumbago* type is further distinguished by being a *four-nucleate* embryo sac at maturity, not an eight-nucleate one. The four haploid nuclei undergo only one mitotic division, leading to an adult embryo sac containing four nuclei (one egg, two synergids, and one polar nucleus). This structural difference (four nuclei vs. eight nuclei) and developmental origin (tetrasporic vs. monosporic) makes *Plumbago* an incorrect match for the "monosporic eight nucleate" description.