2. Totipotency:
What is the Meaning of Totipotency?
Totipotency is the genetic potential of a plant cell to produce the entire plant. In other
words, totipotency is the cell characteristic in which the potential for forming all the cell
types in the adult organism is retained.
3. Expression of Totipotency in Culture:
The basis of tissue culture is to grow large number of cells in a sterile controlled
environment. The cells are obtained from stem, root or other plant parts and are
allowed to grow in culture medium containing mineral nutrients, vitamins and
hormones to encourage cell division and growth. As a result, the cells in culture will
produce an unorganised proliferative mass of cells which is known as callus tissue.
4. cont..
➢ The cells that comprise the callus mass are totipotent.
➢ Thus a callus tissue may be in a broader sense totipotent, i.e., it may be able to regenerated back to
normal plant given certain manipulations of the medium and the cultural environment.
➢ Truly speaking, totipotency of the cell is manifested through the process of differentiation and the
hormones in this process play the major role than any other manipulations.
➢ A typical crown gall tumour cell has the capacity for unlimited growth independent of exogenous
hormones.
➢ It shows totally lack of organ genic differentiation. So such tissue is considered to have
permanently lost the totipotentiality of the parent cells.
➢ In some plant species, the crown gall bacterium (Agrobactenum tumefaciens) induces a special
type of tumour, called teratomas, the cells of which possess the capacity to differentiate shoot buds
and leaves when they are grown in culture for unlimited periods.
➢ Thus it is clear that the mode of expression of totipotency of plant cell in culture varies from plant
to plant and also helps us to understand the process of differentiation in vitro.
5.
6. Importance of Totipotency in Plant Science:
➢ The ultimate objective in plant protoplast, cell and tissue culture is the reconstruction of plants
from the totipotent cell.
➢ Although the process of differentiation is still mysterious in general, the expression of totipotent
cell in culture has provided a lot of information’s.
➢ On the other hand, the totipotentiality of somatic cells has been exploited in vegetative
propagation of many economical, medicinal as well as agriculturally important plant species.
➢ Therefore, from fundamental to applied aspect of plant biology, cellular totipotency is highly
important.
➢ Recent trends of plant tissue culture include genetic modification of plants, production of
homozygous diploid plants through haploid cell culture, somatic hybridization, mutation etc.
➢ The success of all these studies depends upon the expression of totipotency. In many cases,
successful and exciting results have been obtained.
➢ Plant breeders, horticulturists and commercial plant growers are now more interested in plant
tissue culture only for the exploitation of totipotent cells in culture according to their desirable
requirement. Totipotent cells within a bit of callus tissue can be stored in liquid nitrogen for a
long period. Therefore, for germplasm preservation of endangered plant species, totipotency can
be utilized successfully.
