The capacity to generate a whole plant from any cell/explants is called -      

Tissue culture is a technology developed based on the totipotency of plant cells.

 It was learned by scientists, during 1950s, that whole plants could be regenerated from explants, i.e., any part of a plant taken out and grown in a test tube, under sterile conditions in special nutrient media. 

This capacity to generate a whole plant from any cell/explant is called totipotency