Question

Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structures formed at the end of these two events.

Answer 1

Sporogenesis is a process that enables sexual reproduction in plants by making gametes or spores. The terms ‘micro’ means small and ‘mega’ means large. So, the term sporogenesis means spore production.

Complete answer: Microsporogenesis is a process that results in the formation of male gametes, whereas megasporogenesis results in the formation of female gametes. Microsporogenesis or production of microspores is a process that occurs in plants to make pollen grains from the mother pollen cells. The process involves meiotic cell division. Through meiosis, each microspore mother cell in the sporogenous tissue of plants produces four cell clusters called the microspore tetrad. When the anther undergoes the maturity phase, it dehydrates, and thus the clusters of microspore tetrad separate from each other forming the pollen grains. These pollen grains are the male gametes and are much smaller in size than the female gametes. The formation of pollen grains is termed as microsporogenesis. Megasporogenesis, on the other hand, is the process that occurs in plants to make haploid egg or ovum from the diploid megaspore mother cell which is the first cell of the female gametophyte. This process also involves the meiotic cell division. The nucellus in the micropylar region of the plant consists of dense cytoplasm with a prominent nucleus that differentiates into megaspore mother cells. This megaspore mother cell undergoes meiosis and divides transversely forming two cells called dyad. The dyads again divide transversely forming four haploid cells that are called megaspore tetrad. From these four megaspores, only one develops into a female gamete. The female gamete is comparatively larger than the male gamete. Both the processes involve meiotic cell division as the gametes need to be haploid so that when opposite sex gametes fuse they make a diploid zygote. The pollen grain is the result of microsporogenesis and the egg or embryo sac is the result of megasporogenesis.

Note: The final products of both these processes are utilized in the process of fertilization. The male gametes are brought near the female gamete by pollination. This results in the formation of a zygote that has the potential to develop into an individual plant.