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

Abstract

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.

Resin pocket occurrence in Norway spruce depending on tree and climate variables

“…To a degree this contradicts the results of Temnerud et al (1999), who obtained resin pockets from severe bending of saplings in a controlled experiment. However, these mechanical stimuli were different than that one caused by a storm.…”

“…Publications supporting the storms hypothesis were, among others, presented for Norway spruce by Holzmann (1998), Seifert et al (2002), Wernsdörfer et al (2002), and Herb and Becker (2006). Temnerud et al (1999) were able to add further experimental evidence in a bending experiment with Scotch pine (Pinus sylvetris L.) seedlings where they induced similar anatomical structures in consequence of the bending stress as found in resin pockets of adult trees.…”

“…However, recently other wood properties like resin pockets were placed into the centre of attention for this tree species and also other conifers of the economically important genera Picea and Pinus that are prone to the formation of resin pockets. Temnerud et al (1999) proposed to define resin pockets, also called pitch pockets, in accordance with Larson (1994) as an "intercellular circumferentially elongated pocket in the xylem with resin and wound tissue, which is usually occluded by same years as it is formed". The occurrence of resin pockets is a long known phenomenon and a substantial amount of publications deal with the topic because resin pockets are detrimental for timber utilisation (see Gjerdrum and Bernabei, 2007 for a review).…”

A method for three-dimensional stem analysis and its application in a study on the occurrence of resin pockets in Pinus patula

“…Information obtained in this study regarding branches, will be used in another study. Temnerud et al (1999) and Seifert et al (2010), in accordance with Larson (1994), chose to define resin pockets as: "...an intercellular circumferentially elongated pocket in the xylem with resin and wound tissue, which is usually occluded the same year as it is formed." A resin pocket is considered as a defect in some wood products as it decreases the value of timber and veneer and there is a need to understand the occurrence and causes of formation better.…”

Effect of stem guying on the incidence of resin pockets

“…One known controlled experiment was performed by Temnerud et al (1999) who applied bending stresses to 5-year-old Scots pine (Pinus sylvestris L.) trees during dormancy and/or growth. They found that approximately 30% of the stems that were exposed to bending stresses during growth had xylem wounds, whereas those stems exposed during dormancy and non-exposed controls did not exhibit xylem wounds.…”