High Quality Content by WIKIPEDIA articles! Plant callus (plural calluses or calli) is a mass of undifferentiated cells derived from plant tissue (explants) for use in biological research and biotechnology. In plant biology, callus cells are those cells that cover a plant wound. To induce callus formation, plant tissues are surface sterilized and then plated onto in vitro tissue culture medium. Plant hormones, such as auxins, cytokinins, and gibberellins, are supplemented into the medium to initiate callus formation or somatic embryogenesis. Callus tissue initiation has been described for a number of plant taxonomic divisions: