Gymnosperm Reproduction: Male and Female Gametophytes

Vocabulary flashcards covering the cellular structures, developmental stages, and reproductive anatomy of male and female gametophytes in gymnosperms.

Megaspore mother cell (MMC)

A diploid ($2n$) cell that differentiates inside the nucellus (megasporangium) and undergoes meiosis to produce a linear tetrad of four haploid ($n$) megaspores.

Functional megaspore

The single chalazal megaspore that survives after the upper three megaspores degenerate, which expands and undergoes free nuclear division to form the female gametophyte.

Centripetal cellularization

The process of cell wall formation that begins from the outside and progresses inward toward the center, converting the free-nuclear structure into a multicellular endosperm (female gametophyte).

Archegonium

The female reproductive structure differentiated at the micropylar end from archegonial initials, typically consisting of a short neck, a ventral canal cell, and a large egg cell.

Microsporogenesis

The developmental process wherein a diploid ($2n$) microspore mother cell undergoes meiosis inside the microsporangium (pollen sac) to produce a tetrad of four haploid ($n$) microspores.

Prothallial cells

Small, sterile cells formed first during the asymmetric mitotic divisions of the microspore that eventually degenerate; gymnosperms vary in number, with Pinus producing 2 and Cycas producing 1.

Antheridial cell

A cell produced alongside a prothallial cell during early mitotic divisions inside the microspore that divides further to yield a generative cell and a tube cell.

Mature pollen grain

The shedding stage of the male gametophyte in conifers, which is immature and typically composed of 4 cells: two prothallial cells, a generative cell, and a tube cell.

Body cell

A cell formed alongside the stalk cell from the division of the generative cell, which subsequently divides to produce two male gametes (sperm cells or nuclei).

Pollen tube

An elongation formed by the tube cell after pollination, allowing the male gametes to migrate through the ovule toward the female gametophyte to achieve fertilization.