Elementary plant Biochemistry and Biotechnology (2+1)

Callus Culture

• Callus consists of an amorphous or undifferentiated mass of loosely arranged thin-walled parenchyma cells arising from the proliferating cells of the parent tissue.
  
• For callus initiation, transfer the explants aseptically to the semi solid medium and gently press them into the agar in such a way that good contact is made. Radical tips are laid horizontally on the agar whereas stem sections may be placed vertically with one cut end in the agar, to confer good callus.
  
• Within 2-3 weeks, explants should show new growth as pustules or protuberances or as a fine mat across the surface depending on the distribution and mitotic activity of the parenchyma residing in the excised tissues.
  
• Some callus growths are heavily lignified and hard in texture whereas others break easily into small fragments. Most explants produce sufficient callus in an appropriate medium to allow for subculture within 3-7 weeks.
  
• When cultured for several weeks, callus will show signs of ageing. This can be noted as deceleration of growth, necrotic or browning and finally desiccation.
  
• The newly formed callus will be removed from the initial explant at this stage by cutting with the sterile scalpel.
  
• Once well established, most callus cultures will require regular subculture at approximately 4 weeks interval.

Typical steps in callus culture