Introduction to Callus Culture
Higher plant body is multicellular and is made up of highly organised and differentiated structures like stem, leaf, root, etc. different tissue system present in different organs function in a highly coordinated manner. Now, if the organised tissue are diverted into an unorganised proliferation mass of cell by any means, they will form the callus tissue.
In nature, sometimes callus or callus –like tissue is found to form to form in various part of intact plant either due to deep wound or due to some disease. Deep large wound in branches and trunks of intact plants results in the formation of soft mass of unorganised parenchymatous tissues which are rapidly formed on or below the injured surface of the organ concerned. Such callus tissue is known as wound callus. Wound callus is formed by the division of cambium tissues. They may also be formed by the same process from the parenchymatous cells of cortex, phloem and xylem rays. Callus like growth is also stimulated due to some disease caused by Agrobacterium tumefaciens, synchytrium endobioticum and virus, insects etc.
Such callus –like outgrowth is known as gall or tumour. But the callus in tissue culture is produce experimentally from the small excise portion called the explant of any living healthy plant. In culture, the excised plant tissue losses its structural integrity and changes completely to a rapidly proliferative unorganised mass of cells which is called the callus tissue.
What is Callus Tissue?
Callus tissue means an unorganised proliferative mass of cells produced from isolated plant cells, tissues or organs when grown aspically on artificial nutrient medium in glass vials under controlled experimental conditions.