SEASONAL-VARIATION IN TRAUMATIC RESIN CANAL FORMATION IN CHAMAECYPARIS-OBTUSA PHLOEM

Trunks of Chamaecyparis obtusa were injured to examine seasonal differ ences in traumatic resin canal formation in secondary phloem. Even aft er wounding during winter, differentiation of axial parenchyma into ep ithelium was initiated, and vertical resin canals formed. After winter wounding, resin canal development was slower and the tangential exten t of resin canals was narrower than after spring wounding, and it took one to two months until resin secretion began. After spring wounding, the sites of resin canal formation were the 1- and 2-year-old annual rings of phloem. In August, the location of resin canal formation shif ted into the current and 1-year-old annual ring. Resin canals never fo rmed in secondary phloem areas that were 3 or more years old. In C. ob tusa trunks that are affected by the resinous stem canker, numerous ta ngential lines of resin canals are found throughout the phloem, not ju st recent and 1- to 2-year-old phloem. The present research indicates that these many lines of resin canals were not formed at one time, and that the stimuli that induce traumatic resin canals must occur repeat edly over many years. The data on artificial wounding effects are usef ul for understanding resinous stem canker.