Question

In animals, mitotic cell division is only seen in the diploid somatic cells. Against this, the plants can show mitotic divisions in both haploid and diploid cells. From your recollection of examples of alternation of generations in plants identify plant species and stages at which mitosis is seen in haploid cells.

Answer 1

Hint: Mitosis was first observed by Strasburger in a plant cell and by Walter in an animal Cell. The termite tosses were given by Walter Fleming. My tosses are also called somatic cell division, which causes it usually occurs in the somatic cells of the animal body. It also occurs in the gonads for the multiplication of undifferentiated germ cells. It occurs in the dividing meristematic tissue and also in leaves, Flowers and fruits.

Complete Answer:
- In plants formation of haploid and diploid bodies occur because both the haploid and diploid cells are able to divide and produce by the mitosis. The haploid plant body in the plant is known as gametophytic plant body.
- It produces gametes by the process known as my tosses or equation division. After fertilisation, the diploid zygote also divides by the process of equation and division or can be called as my tosses to produce the diploid that contains 2n number of chromosomes and is called a sporophytic plant body.
- The diploid sporophyte undergoes meiosis and produces haploid spores and those haploid spores divide by mitosis to form a haploid plant body again.
- So, during the life cycle of a plant that undergoes sexual reproduction there occurs alternation of generation between gametes producing haploid gametophyte and spore producing diploid sporophyte.
- The common example exhibiting this is the case of haploid generation of bryophytes. The dominant phase of the bryophytes is free living gametophyte. The gametophyte is a haploid stage of bryophytes that generates gametes by the process of mitosis.
- So, it is called a gametophyte. This is also termed as haplo- diplontic life cycle as haploid gametophyte produces diploid sporophyte.
- Alternation of generation is also exhibited by the pteridophytes and some algae such as Ectocarpus, Polysiphonia, Kelps are haplo diplontic.

Note:
- In bryophytes, the dominant phase is the independent, photosynthetic, thalloid or erect haploid gametophyte and it alternates with the short-lived multicellular sporophyte totally or partially dependent on the gametophyte for its anchorage and nutrition.
- In pteridophytes, the dominant phase is represented by the sporophyte which is a diploid, independent photosynthetic vascular plant body. It alternates with multicellular, independent but short-lived haploid gametophyte.