(a) : Plant tissue culture, also called micro­ propagation, is the growth of plant cells outside the plant body in a suitable culture medium which contains mixture of nutrients in solid or liquid form, under controlled environmental condition. Tissue culture technique is based on totipotent nature of plant cell or phenomenon of totipotency $i.e.$, each and every plant cell has inherent capacity to develop into complete plant. The entirely vegetatively produced descendents of somatic cells are collectively called clone. They are genetically identical to parents.