CBSE Class 9 Answered

Plant tissue culture works on the basis of totipotency. It is the ability of a plant cell to form the complete plant through dedifferentiation and redifferentiation.

It involves following steps:

1.  Selection of source plant- The plant which has to be cultured in vitro is selected.

2. Primary treatment

• Isolation of explant- Explant is any part of plant excised out for tissue culture.
• Sterilization of explant- Explant is surface sterilized so as to avoid contamination.
• Inoculation of explant- The explant is inoculated on the nutrient medium. For plant tissue culture, the most common medium used is MS media. 
• Incubation: After inoculation, the cultures are incubated so as to provide proper conditions for their growth and regeneration like temperature, moisture etc.

3. Reproduction/Multiplication (Initiation of callus): Callus is a mass of undifferentiated cells formed by the dedifferentiation of plant cells or the explant. Callus further regenerates to form roots and shoots and eventually the complete plant.

4.  Shooting and rooting

• Sub-culturing: The cultured cells or tissues are transferred regularly to new nutrient medium and this is called subculturing.
• Regeneration: Regeneration is the formation of organized structures like roots, shoots, flower buds etc from the cultured cells

5. Primary Hardening: The plantlets are removed from the cultures and prepared for soil transfer and this transfer to fields is known as hardening.