The number of viable seeds produced by the tomato plant through sexual reproduction = 240

(a) The minimum number of pollen grains that must have been involved in the pollination of its pistil are 240 because each pollen grain contains two male gametes. Out of these two gametes, one fuses with polar nuclei and forms endosperm, while, the other male gamete fuses with the egg cell to form the zygote that eventually give rise to seeds. Therefore, in order to obtain 240 seeds, number of pollen grains needed would be 240.

(b) The minimum number of ovules involved in this process would be 240, as the number of viable seeds is 240. After fertilisation, the ovary turns into fruit and the ovules turn into seeds. Therefore, the number of ovules corresponds to the number of seeds formed.

(c) During the process of gametogenesis, 240 megaspore mother cells are involved as only one megaspore of the tetrad becomes functional and develops further and the rest three megaspores get degenerated.

(d) In the above case, 60 microspore mother cells must have undergone reduction division prior to dehiscence of anther, as each microspore mother cell would give rise to 4 microspores. Since 1 microspore mother cell would produce 4 microspores, therefore, to obtain 240 microspores, there must be 60 microspore mother cells.

(e) The number of male gametes involved in seed formation would be 240 as each male gamete will fuse with one egg nuclei to form zygote, which will further give rise to the seed.