Phellogen Regeneration in Injured Peach Tree Bark

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Abstract
Injury to peach bark phellogen leads to the generation of new tissues and the re-establishment of meristematic continuity. Two types of tissue changes after wounding were identified and quantified in bark of seven peach clones: (1) cell wall modifications (lignification and suberization) of tissues present at the time of wounding, and (2) generation of the new phellogen and its derivatives. Tissue responses were quantified with a microscope photometer using selective histochemistry and autofluorescence to detect lignin and suberin deposition over time. Suberin continuity was re-established via suberin deposition in a layer of cells, present at the time of wounding, approximately 800 μm internal to the wound surface. Phellogen continuity was re-established immediately internal to and abutting the suberized tissue. The new phellogen gave rise to suberized phellem which, in its outward expansion, crushed the suberized boundary zone tissue formed earlier. All injured peach clones produced the same sequence of tissue changes, although timing and degree of response varied with clone and time of year.