NEET BIOLOGY

Detailed explanation-1: -The nucleus of the microspore divides mitotically into a vegetative and a generative cell, the latter of which divides into two sperm nuclei.

Detailed explanation-2: -Each pollen mother cell(PMC), by a meiotic division, gives rise to a group of four haploid microspores. Thus, 1616 pollen mother cells undergo meiotic divisions to produce 6464 pollen grains.

Detailed explanation-3: -One diploid microspore mother cells by meiosis forms 4 tetrads of haploid microspores which become 4 pollen grains. Therefore, for the formation of 200 pollen grains 50 meiosis in 50 microspore mother cells are required (2004=50 ).

Detailed explanation-4: -In the process of male gamete formation, a pollen mother cell undergoes meiosis to form a tetrad of microspores enclosed in callose (1, 3- glucan; Figure 12.1). Dissolution of the callose occurs by enzymes released from the tapetal cells, dispersing the individual 1N microspores.