Flower Structure Gametogenesis

The trap: NEET frequently tests whether you can distinguish parts of a flower that look similar in name but differ in function — particularly confusing microsporogenesis (pollen formation) with megasporogenesis (embryo sac formation), and mixing up the products of each process.

A typical flower has four whorls: calyx (sepals), corolla (petals), androecium (stamens), and gynoecium (carpels). The androecium is the male reproductive unit; each stamen consists of a filament and an anther. The gynoecium is the female unit; each carpel has a stigma, style, and ovary (NCERT Class 12 Biology Chapter 1, page 2).

Microsporogenesis: Inside the anther's microsporangia, microspore mother cells (2n) undergo meiosis to produce tetrads of microspores (n). Each microspore develops into a pollen grain — a 2-celled (generative + vegetative) or 3-celled structure at shedding.

Megasporogenesis: Inside the ovule's nucellus, a megaspore mother cell (2n) undergoes meiosis to form four megaspores. Typically only one (chalazal) is functional — the other three degenerate. The functional megaspore undergoes three mitotic divisions to produce a 7-celled, 8-nucleate embryo sac (Polygonum type): 3 antipodals, 2 synergids, 1 egg cell, and a central cell with 2 polar nuclei.

Watch-out for NEET: The number of pollen grains from one microspore mother cell is 4 (meiosis produces 4 functional microspores). From one megaspore mother cell, only 1 functional megaspore survives. Questions often swap these numbers or ask about the ploidy at each stage.

---