Question

how many chromosomes microspore mother cell have atG1,G2, interkinesis .if polen have 20 chromosomes at the end of meiosis 2​

Answer 1

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The inner diploid sporogenous tissue of each microsporangium first undergoes mitotic divisions to increase the cell number and then differentiates into microspore/pollen mother cell. Being the product of mitosis in diploid cells, microspore mother cells are diploid i.e. carry two complete sets of chromosomes. Double fertilization is characterized by fusion of one male gamete fuses with egg nucleus (syngamy) to form the diploid embryo and that of other with diploid secondary nucleus/central cell (triple fusion) to form triploid primary endosperm nucleus which in turn divides to form large nutritive endosperm. This makes endosperm triploid being the product of triple fusion between the diploid secondary nucleus and haploid male gamete. Therefore, if microspore mother cell has 2n= 24 chromosomes, the triploid endosperm will have 3n= 36 chromosomes. Thus, the correct answer is option A.