Wound-induced lignin and suberin deposition in a woody angiosperm (Eucalyptus gunnii Hook): Histochemistry of early changes in young plants

A simple system was developed to investigate the deposition of lignin and synthesis occurring in response to mechanical wounding in the woody angiosperm Eucalyptus gunnii Hook. The spatiotemporal deposition of these phenolic polymers was histochemically characterized in stem tissue through a combination of fluorescent microscopy and specific stains. Lignin and suberin deposition was detectable 24 h post wounding in the ''xylem wound zone'' and by 3 days post wounding in the ''bark wound zone'' where a well-developed necrophylactic (wound) periderm could be observed by 7 days post wounding. Close examination suggests that the spatial reinforcement of cell walls with lignin and/or suberin is carefully orchestrated so as to rapidly produce an effective protective barrier. Specific lignin colour reactions indicate that the lignin formed in response to wounding in both the bark and xylem wound zones is relatively poor in syringyl monomers as compared to that of ''developmental'' xylem lignin.