Write a note on callus culture.

Hint: Callus culture is a culture done in laboratories for genetically modified plants and crops.Callus culture is the culture of dedifferentiated plant cells induced on media usually containing relatively high auxin concentrations or a combination of auxin and cytokinin under in vitro conditions.

Complete step by step answer:
-Plant callus is a growing mass of unorganized plant parenchyma cells.
-In living plants, callus cells are those cells that cover a plant wound.
-In biological research and biotechnology callus formation is induced from plant tissue samples (explants) after surface sterilization and plating onto tissue culture medium in vitro (in a closed culture vessel such as a Petri dish).
-The culture medium is supplemented with plant growth regulators, such as auxin, cytokinin, and gibberellin, to initiate callus formation or somatic embryogenesis.
-A callus cell culture is usually sustained on gel medium. Callus induction medium consists of agar and a mixture of macronutrients and micronutrients for the given cell type.
-There are several types of basal salt mixtures used in plant tissue culture, but most notably modified Murashige and Skoog medium, White's medium, and woody plant medium.
-Vitamins are also provided to enhance growth such as Gamborg B5 vitamins.
For plant cells, enrichment with nitrogen, phosphorus, and potassium is especially important. Plant callus is usually derived from somatic tissues.
-The tissues used to initiate callus formation depend on plant species and which tissues are available for explant culture.
-The cells that give rise to callus and somatic embryos usually undergo rapid division or are partially undifferentiated such as meristematic tissue.
-Plant hormones are used to initiate callus growth.

Note:
In alfalfa, Medicago truncatula, however callus and somatic embryos are derived from mesophyll cells that undergo dedifferentiation.