Where does meiosis take place during microsporogenesis?

The correct answer is Option (4) → In microspore mother cells

Microsporogenesis is the formation of microspores inside the anther. In a young microsporangium the cells of the sporogenous tissue each act as a pollen mother cell (microspore mother cell). Each of these cells divides by meiosis and gives a tetrad of four haploid microspores.

Option (1) In pollen grains — Incorrect. Pollen grains are formed after meiosis. The microspores of a tetrad separate and develop into pollen grains, so meiosis does not take place in them.

Option (2) In ovule — Incorrect. The ovule is the female part. The meiosis that takes place in the ovule forms megaspores (megasporogenesis), not microspores.

Option (3) In nucellus — Incorrect. The nucellus is the tissue of the ovule. The megaspore mother cell that lies in it undergoes meiosis during megasporogenesis, not microsporogenesis.

Option (4) In microspore mother cells — Correct. The microspore mother cell, also called the pollen mother cell (PMC), is the diploid cell that undergoes meiosis to form the microspore tetrad.

NCERT Extract:
Stamen, Microsporangium and Pollen Grain – “… Microsporogenesis : As the anther develops, the cells of the sporogenous tissue undergo meiotic divisions to form microspore tetrads. … As each cell of the sporogenous tissue is capable of giving rise to a microspore tetrad. Each one is a potential pollen or microspore mother cell. The process of formation of microspores from a pollen mother cell (PMC) through meiosis is called microsporogenesis. The microspores, as they are formed, are arranged in a cluster of four cells–the microspore tetrad (Figure 1.3a).”