Elementary plant Biochemistry and Biotechnology (2+1)

Explant and explant selection

• A plant organ or piece of tissue used to initiate a culture. Almost all parts of plant are amenable to in vitro plant regeneration (E.g. Tobacco). However, in certain plants some organs may be more regenerative than the others (e. g. in Glycine max, the hypocotyls exhibits higher potentiality for shoot formation than the root segments).
The regenerability of an explant is influenced by several factors:

1. Organ from which it is derived.
2. The physiological state of explant
3. Size of the explant
4. Orientation of the explant on the medium and
5. Its inoculation density.

Sterilization and its techniques

• Sterilization is the process of inactivating or removing all living organisms from a substance or surface. Different kinds of sterilization procedures were adapted in plant tissue culture. They are,

Heating

• Dry heat (e.g. Hot air oven) is used for glassware and Steam or moist or wet heat (e.g. Autoclave) is used for sterilization of media and fermenter vessels.

Radiation

• UV radiation and high efficiency particulate air (HEPA) filter in laminar air-flow chamber used for sterilization of transfer area.

Chemicals

• 95 % ethanol used for sterilizing forceps, scalpels, needles etc., Hypochlorite solutions (sodium or calcium) and antibiotics are used as sterilizing agents to disinfect plant tissues.

Ultra filtration

• The solution of thermolabile compounds (e.g. vitamins, antibiotics etc) is sterilized by membrane filtration.

Explants used in Micropropagation

• Different kinds of explants were used in micropropagation. For example, in case of orchids, shoot tip (Anacamptis pyramidalis, Aranthera, Calanthe, Dendrobium), axillary bud (Aranda, Brassocattleya, Cattleya, Laelia), inflorescence segment (Aranda, Ascofinetia, Neostylis, Vascostylis), lateral bud (Cattleya, Rhynocostylis gigantean), leaf base (Cattleya), leaf tip (Cattleya, Epidendrum), shoot tip (Cymbidium, Dendrobium, Odontioda, Odontonia), nodal segment (Dendrobium), flower stalk segment (Dendrobium, Phalaenopsis) and root tips (Neottia, Vanilla) are being used in micropropagation.