In this article we will discuss about the concept of callus and suspension culture with the help of suitable diagram.
Callus is a mass of undifferentiated cells formed due to cell division. It is an unorganised mass grown on a medium consisting of gelling agent agar. This medium also contains auxin and a small amount of cytokine. When cells are placed in such a medium they become meristematic. A callus is obtained in a period of 2-3 weeks. Such a callus is known as callus culture.
Suspension culture is grown on a liquid medium. It is a mass of free cells or small masses of cells. This kind of culture is to be kept in a shaker or at 100 – 250 rpm so that there is constant aeration, mixing of medium and cell aggregates break into smaller groups. It is been observed that suspension cultures grow faster than the callus cultures (Fig. 7).
With the passage of time following events can be observed:
a. Increase in tissue or cell biomass
b. Nutrient level decreases in the medium
c. Volume of medium declines due to evaporation.
Due to the above mentioned reasons, if the culture is kept in the same medium the tissues will die in due course of time. To overcome this the cultured cells or tissues should be transferred regularly to new culture vessels containing fresh medium. This is known as sub culturing (Fig. 8). In callus culturing this procedure is generally done once in every 4-6 weeks, whereas in culturing this is done once in every 3-14 days.
These cultures can be used for isolation of protoplast, regeneration of protoplast, production of transgenic plants and isolation of bio-chemicals.
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