Question

For the formation of 50 seeds how many minimum meiotic divisions are necessary?

Answer 1

For formation of seeds, both male and female contribute. Hence, we have to consider meiotic divisions required for male gamete as well as female gamete.
For calculation of meiotic divisions taking place in male: 1 Microspore mother cell (PMC) undergoes 1 meiosis to give rise to 1 tetrad. 1 tetrad gives rise to 4 pollen grains. Each pollen grains undergoes mitosis twice (first when vegetative and generative nuclei are formed and second when 2 male gametes are formed from generative nucleus). Hence, total 1 meiosis produces 4 pollen grains. And only one pollen grain participates in fertilisation. Therefore, 1/4 th of total number of seeds are the number of divisions.
For calculation of meiotic divisions taking place in female: 1 Megaspore mother cell (MMC) undergoes 1 meiosis to give rise to linear tetrad. Most of the plants show monosporic development. So, 3 of them degenerate and only 1 is functional. This functional megaspore divides mitotically thrice to give rise to embryo sac. Hence, 1 meiosis produces 1 egg cell. So, number of seeds= number of meiotic divisions.

Total number of divisions= (50/4) + (50/1)= 12.5 + 50 = 62.5.
But there cannot be divisions in decimals. Hence, 63 meiotic divisions are required for production of 50 seeds.