fracture toughness; mode I critical stress intensity factor; fracture mechanics; beech wood

The aim of this research was to examine the content of catechin in normal and traumatic structures of beechwood by high performance liquid chromatography (HPLC). Two discs were sawn from each of six harvested trees. The first disc was taken from the lower, wounded part and the second one from the upper part of each stem. Discs containing the bases of living and dead branches were taken from the crown. Samples of wound-wood, reaction zones, sapwood, as well as living and dead knots, were sampled from discs. Samples were milled and then extracted sequentially by cyclohexane and methanol/water in a Soxhlet apparatus. A method for the separation of catechins from extracts was developed for the present chromatographic investigation. Statistical analysis did not reveal significant differences in total or hydrophilic extractives, nor in the content of catechin among the investigated trees. The content of hydrophilic extractives and catechin were significantly different among the investigated categories of wood tissues. Wound-wood and knot extracts contained the highest amount of this flava-3-ol. Reaction zones contained higher amounts of catechin than discolored wood, but less than sapwood. The extracts of discolored wood showed the lowest amounts of catechin. Sapwood samples that originated from wounded discs exhibited significantly higher contents of catechin than normal sapwood from upper discs. Accumulation of bioactive compound catechin in wound-wood, sapwood and knots is considered to be an important part of the survival strategy of living trees.

Abstract licence: CC BY

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