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

Abstract

The reddish-violet heartwood of Juniperus virginiana L. contains irregularly distributed and longitudinally oriented streaks of light-coloured 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 UV-spectroscopic analysis revealed a secondary metabolism particularly of phenolic compounds in the pit membranes of tracheids during “included sapwood” formation, whereas the reddish-violet 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, α-cedrene, widdrol, thujopsene and cuparene increased in “included sapwood” compared to sapwood. As opposed to the reddish-violet heartwood compounds, these sesquiterpenes turned out to be highly toxic against a brown-rot 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.