Plant tissue culture and micropropagation

Plant tissue culture is the technique of maintaining and growing aseptically plant cells, tissues or organs on artificial medium in test tube under controlled environmental conditions. The part which is cultured is called explant, i.e., any part of a plant taken out and grown in a test tube, under sterile conditions in special nutrient media. Plant tissue culture relies on the fact that the plants have a capacity to generate a whole plant from any cell/explant (cellular totipotency). Single cells, plant cells without cell walls (protoplasts), pieces of leaves, stems or roots, embryo, anther can be used to generate a new plant.

What we need to culture plant explants in vitro (from Latin “within glasses)?

1. Nutrient Medium: The composition of plant tissue culture medium should supply all cell growth needs and can vary depending upon the type of plant tissues or cell that are used for culture. A typical nutrient medium contain inorganic salts (both micro and macro elements), a energy source (usually sucrose), vitamins (e.g., nicotonic acid, thiamine, myoinositol), amino acids and growth regulators (plant hormones) -e.g., auxins like 2,4-D and cytokinins such as BAP = benzlaminopurine and gibberellins).An optimum pH (usually 5.7) is also very important. The medium can be liquid or solid. Usually a gelling agent agar (a polysaccharide obtained from a red algae Gelidium amansi) is added to the liquid medium for its solidification.

2. Aseptic Conditions (Sterilization). Nutrient medium contains sugar which increases growth of microorganisms (bacteria and fungi). These microbes compete with growing tissue and finally can kill it. It is essential to maintain aseptic conditions of tissue culture. The plant material must first be surface sterilized to remove any bacteria or fungal spores that are present.The aim is to kill all microorganisms, but at the same time not cause any adverse damage to the plant material. The explants are transferred into the suitable sterilized nutrient medium in culture vessels at sterile conditions under HEPA filtered air provided by a laminar flow cabinet.

3. Growth conditions. Growing the culture in the growth chamber or plant tissue culture room, having the appropriate physical condition -artificial light; 16 hours of photoperiod, temperature (26°C) and relative humidity (50-60%) is required.

Practical Applications of Plant Tissue Culture:

  • Micropropagation is the tissue culture technique used for rapid vegetative multiplication of ornamental plants and fruit trees. This method of tissue culture produces several plants. Each of these plants will be genetically identical to the original plant from where they were grown. Well rooted plants are removed from culture vessels and transferred in controlled, but not sterile environmental condition to hardening and subsequent transplantation in the field.

Advantages of micropropagation:

– Rapid multiplication of plants within a short period and on small space.

– Plants are obtained under controlled conditions, independent of seasons.

-Sterile plants or plants which cannot maintain their characters by sexual reproduction are multiplied by this method.

-The rare plant and endangered species are multiplied by this method and such plants are saved.

-Production of virus free plants like potato, sugarcane, banana and apple for horticulture and agriculture.

  • Large-scale growth of plant cells in liquid culture in bioreactors for production of valuable compounds
  • Cross distantly related species by protoplast fusion and regeneration of the novel hybrid.
  • Rapid in vitro selection of stress tolerant plants –salt, drought, heavy metal, low temperature, herbicide resistant
  • Regenerate the whole plants from plant cells that have been genetically modified.