Wound-induced callus formation has long been observed and used in various contexts from debarking of trees (Stobbe et al., 2002) to horticultural use of propagation (Cline and Neely, 1983). These calli often accumulate phytoalexins and pathogen-related proteins (Bostock and Stermer, 1989) and thus are thought to prevent infection as well as water loss. Wound-induced callus derive from various cell types, including vascular cells, cortical cells, and pith cells. In some cases, wound-induced calli regenerate new organs or new tissues, suggesting that they are highly pluripotent (Stobbe et al., 2002).