Induction of Resin Pockets in Seedlings of Pinus sylvestris L. by Mechanical Bending Stress during Growth

Abstract

Summary Mechanical bending stress due to wind exposure has been suggested to be of major importance for induction of resin pockets in gymnosperm trees. In this study, this idea was tested experimentally by applying bending stress to 1-year-old internodes of five-year-old Pinus sylvestris L. seedlings during dormancy and/or growth. The stems were bent manually to 30° from their original upright position at regular intervals. About 30% of the stems that were bent during growth were wounded in the xylem, whereas no wounding was observed in control stems or stems bent during dormancy. Similarity of these wounds to naturally-occurring resin pockets leads us to conclude that exposure of seedlings to mechanical bending stress due to wind during growth can be a source of formation of resin pockets.