Wednesday, 12 August 2015

Cellular Totipotency

Cellular totipotency is the ability of a living somatic cell to form the complete organism. A cell is totipotent because it has a complete genetic information in its nucleus. Somatic cells during their maturation the cells undergo differentiation ( specialized cells for a particular function). Differentiated cells not showing division. Under special circumstances differentiated cells will change into immature cells called dedifferentiation. After dedifferentiation cells will start to multiply.
Totipotency can be easily demonstrated in plant cells.
                                                                                    Cellular totipotency was first proposed by German botanist Haberlandt in 1902. He thought if every somatic cell has the full genetic material then why this cell should not be able to produce whole organism. However he failed to grow new plants from isolated cells of green leaves. He failed due to

1) Lack of aseptic conditions
2) Lack of proper nutrient medium

The two defects removed by White (1932). The scientist successfully grew tomato roots in culture medium. In 1939,  three scientist ( White, Gautheret, Nobecourt ) were independently able to grow callus in tissue culture. Callus is unorganized mass of cells. Skoog and Miller (1957) discovered that callus can be made to develop shoots and roots through changing the ratio of harmones ( IAA and cytokinin). The phenomena is called morphogensis. Cellular totipotency was demonstrate first time by Steward et al ( et al means co-workers) in 1957. they took 2 mg pieces from phloem of carrot roots. These pieces or explants were made up of mature nondividing cells. They placed these explants in liquid culture medium containing coconut milk. There was an active growth and division of cells. After shaking the cells tend to form clusters. Clusters differentiated and formed initials of roots. In a semisolid medium, each developed shoot and gave rise to a plantlets or a small plant.

Advantages:-  1) Quick propagation of useful plants.
                         2) Raising rare plants which are difficult to grow from seeds.
                         3) Multiplying sterile hybrids.
                         4) Rapid production of new verieties.
                         5) Production of virus free plants.
                         6) Production of chemical resistant varieties.
                         7) Reducing the period of formation of new varieties.
                         8) Introducing mutations and selecting mutants.












                                                       
                                                       
                                                                 

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