Biological and chemical characteristics of "included sapwood" of Juniperus virginiana L.

The reddishviolet heartwood of Juniperus virginiana L. contains irregularly distributed and longitudinally oriented streaks of lightcoloured wood, described as included sapwood. A histological study revealed that a blockage of the rays, which is caused by wounds often associated with tiny shakes, branch stubs and included bark, may lead to this anomaly. A study of fresh wood immediately after felling of the trees showed that included sapwood lacks physiological activity similar to the adjacent normal heartwood. Cellular UVspectroscopic analysis revealed a secondary metabolism particularly of phenolic compounds in the pit membranes of tracheids during included sapwood formation, whereas the reddishviolet flavonoid compounds do not develop in this anomalous wood. Chemical analyses of petrol ether, diethyl ether, acetone and ethanol/water extracts of sapwood, included sapwood and heartwood showed that the accessory compounds cedrol, acedrene, widdrol, thujopsene and cuparene increased in included sapwood compared to sapwood. As opposed to the reddishviolet heartwood compounds, these sesquiterpenes turned out to be highly toxic against a brownrot fungus in a bioassay. These findings justify defining included sapwood as a heartwood anomaly, since the important wood characteristics of this tissue obey the definition of heartwood rather than sapwood. This anomaly should no longer be a reason to exclude this type of wood from commercial utilisation.