Q.Trace the sequence of events, starting from a microspore mother cell, that leads to the formation of a pollen grain.

Each diploid microspore mother cell undergoes meiosis to give four haploid microspores in a tetrad, which later separate and mature into pollen grains.

The sporogenous tissue within a young microsporangium differentiates into microspore mother cells (pollen mother cells, PMCs), which are diploid. Each PMC undergoes meiosis (reductional division), so one PMC gives rise to four haploid microspores arranged together as a microspore tetrad. As the anther matures, the microspores of a tetrad separate from one another and become free, individual microspores. Each microspore then develops into a pollen grain: its nucleus divides mitotically once to form a large vegetative (tube) cell and a smaller generative cell. At this stage pollen is generally shed. In many species the generative cell divides again (sometimes before shedding, sometimes only after the pollen tube begins to grow) to produce two non-motile male gametes, so a pollen grain represents the immature (or, once the generative cell has divided, the mature) male gametophyte.

Trace the sequence as a chain: PMC -> meiosis -> tetrad -> separation -> pollen grain -> generative-cell division -> male gametes.

Saying meiosis happens 'in the pollen grain' rather than in the PMC before the tetrad stage; forgetting that microspores must separate from the tetrad before further development.