1. <botany> Undifferentiated plant tissue produced at wound edge callus tissue can be grown in vitro and induced to differentiate by varying the ratio of the hormones auxin and cytokinin in the medium.

2. <pathology> Mass of new bony trabeculae and cartilaginous tissue formed by osteoblasts early in the healing of a bone fracture.

This entry appears with permission from the Dictionary of Cell and Molecular Biology

(11 Mar 2008)