Q.Write a short note on Sterilization of Explants in plant tissue culture.

Explant sterilization removes surface contamination through washing, ethanol treatment, a sterilant, and sterile rinsing under aseptic conditions.

In plant tissue culture, the explant (the piece of plant tissue used to start the culture) must be completely free of surface microbial contamination -- bacteria and fungi -- before it is placed on the nutrient medium, since any contaminant would rapidly overgrow the culture. The standard sterilization procedure involves the following steps:

1. Washing: the explant is first washed thoroughly under running tap water, sometimes with a mild detergent, to remove adhering dust, soil and surface debris.
2. Ethanol treatment: it is then briefly dipped in 70% ethanol for a short period (a few seconds to about a minute), which acts as a quick surface disinfectant.
3. Treatment with a sterilant: the explant is next treated with a suitable chemical sterilant for a controlled duration (typically a few minutes) -- most commonly a dilute solution of sodium hypochlorite (NaOCl), such as diluted commercial bleach, or mercuric chloride (HgCl2). These agents kill surface-adhering bacteria and fungal spores without excessively damaging the plant tissue if the concentration and exposure time are properly controlled. …