Traumatic Resin Canal Formation as a Marker of Xylem Growth

Anatomical changes in traumatic resin canal formation induced in Tsuga sieboldii by metal pins were examined periodically after insertion. Symptoms of traumatic resin canal formation were first observed in the zone of xylem mother cells within a few days after pinning, and there was a close correlation between these resin canals and the formation of abnormal tissue at the pinned point. Cambial initials at the time of pinning appeared to be in the vicinity of epithelial cells on the cambial side of traumatic resin canals. The validity of using easily discernible, pin-induced traumatic resin canals, instead of minute abnormal tissues, for marking xylem growth is discussed in the light of these findings. Forest Sci. 29:653-659.