Question

A flower of brinjal plant following the process of sexual reproduction produces 360 viable seeds. Answer the following questions giving reasons.
(a) How many ovules are minimally involved?
(b) How many megaspore mother cells are involved?
(c) What is the minimum number of pollen grains that must land on stigma for pollination?
(d) How many male gametes are involved in the above case?
(e) How many microspore mother cells must have undergone reduction division prior to dehiscence of anther in the above case?

Answer 1

In process of sexual reproduction, a complex life cycle is involved in which a single set of chromosomes (haploid) combines a gamete (such as a sperm or egg cell) with another to create an entity composed of cells with two sets of chromosomes (diploid).

Complete answer:
The no. of viable seeds produced by the brinjal plant through sexual reproduction as stated in question = 360
(a) Fruit is formed from mature ovary. The ovary grows into a fruit after fertilization and the ovules develop into seeds. If the number of viable seeds is 360, the number of ovules minimally involved in this process will be 360. The number of ovules is then equal to the number of seeds that have been produced.
(b) 360 megaspore mother cells are active during the gametogenesis process when only one megaspore of the tetrad remains functional and grows more and the other three megaspores degenerate.
(c) The minimum number of pollen grains to land under the pollination stigma is 360 and there are two male gametes in each pollen grain. One fuses with polar nuclei and forms endosperm from these two gametes, while the other male gamete fuses with the egg cell to create the zygote that finally gives birth to the seeds. Therefore the amount of pollen grains required will be 360 to obtain 360 seeds.
(d) When each male gamete fuses with one egg nucleus to form zygote, the number of male gametes involved in seed forming will be 360, which would further give birth to the seed.
(e) In the above example, prior to the dehiscence of anther, 90 microspore mother cells (360/4) would have undergone reduction division, as each microspore mother cell will give birth to 4 microspores. Therefore to acquire 360 microspores, there must be 90 microspore mother cells, since 1 microspore mother cell would contain 4 microspores.

Note: Within the flower and the seeds that are inside a fruit, these sex organs in plants are carried. Angiosperms or flowering plants are called such plants as they reproduce by the method of sexual reproduction. Most plants produce both male and female reproductive organs in the flowers.