A flower of tomato plant following the process of sexual reproduction produces 200 viable seeds.

Answer the following questions giving reasons :

(a) What would have been the minimum number of ovules present in pre-pollinated pistil ?

(b) How many microscope mother cells would minimally be required to produce requisite number of pollen grains ?

(c) How many pollen grains must have minimally pollinated the carple ?

(d) How many male gametes would have used to produce these 200 viable seeds ?

(e) How many megaspore mother cells were required in this process ?

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#### Solution

The number of viable seeds produced by the tomato plant through sexual reproduction = 200

(a) The number of ovules minimally involved in this process would be 200 as the number of viable seeds are 200. After fertilisation, the ovary turns into a fruit and the ovule turn into a seed. Thus, the number of ovules would correspond to number of seeds formed.

(b) In the above case, 50 microspore mother cells must have undergone reduction division prior to dehiscence of anther, as each microspore mother cell would give rise to 4 microspores. One microspore mother cell would produce 4 microspores; therefore, to obtain 200 microspores, there should be 50 microspore mother cells.

(c) The minimum number of pollen grains that must land on stigma for pollination are 200 because each pollen grain contains 2 male gametes. Out of theses 2 gametes, 1 fuses with polar nuclei and forms endosperm, while the other male gamete fuses with the egg cell to form the zygote, which eventually gives rise to seeds. Therefore, in order to obtain 200 seeds, the number of pollen grains needed would be 200.

(d) The number of male gametes involved in seed formation would be 200 as each male gamete will fuse with 1 egg nuclei to form zygote, which will further give rise to the seed.

(e) In the process of gametogenesis, 200 megaspore mother cells would be involved. Only one megaspore of the tetrad becomes functional and develops further and the rest three are degenerated.